With commentaries by Chinese and Japanese authors from the Third through the Twentieth century
The Complete Chinese Text with an Annotated Translation
by Paul U. Unschuld
University of California Press
Nan Jing
The
Chinese Medical Classics
Nan Jing
The Classic of Difficult Issues
With commentaries by Chinese and Japanese authors from the Third through the Twentieth century
The Complete Chinese Text with an Annotated Translation
by Paul U. Unschuld
University of California Press
University of California Press, one of the most distinguished university presses in the United States, enriches lives around the world by advancing scholarship in the humanities, social sciences, and natural sciences. Its activities are supported by the UC Press Foundation and by philanthropic contributions from individuals and institutions. For more information, visit www.ucpress.edu.
University of California Press Oakland, California
Index to Prolegomena, Commentaries, and Notes / 619
Comparative Studies of Health Systems and Medical Care / 639
PART I. PROLEGOMENA
Introductory Remarks
The Nan jing is an ancient Chinese medical classic; it was compiled, probably, at some time during the first or second century CE. For the past eight or nine centuries, the Nan jing has been overshadowed by the reputation and authority of the “original” classic, the Huang Di nei jing (“The Yellow Thearch’s Inner Classic”) with its two largely different segments, the Huang Di nei jing Su wen (or Su wen ) and the Huang Di nei jing Ling shu (or Ling shu ). The present edition of the Nan jing combines a translation of its textus receptus and of selected commentaries by twenty Chinese and Japanese authors of the past seventeen centuries with an interpretation by this author. One of its goals is to demonstrate that the Nan jing should once again (as was the case until early the second millennium) be regarded as a significant and innovative work that marks the apex, and also the conclusion, of the developmental phase of the conceptual system known as the medicine of systematic correspondence.
The contents of the Nei jing texts, in contrast, should be appreciated as a collection of extremely valuable transitory stages in this developmental phase—valuable because they reflect various historical steps as well as a wide range of diverging (and even contradictory) theoretical arguments.1 These arguments characterize the genesis of a system of therapeutic ideas and practices which has a formative period that can be traced from its first extant documented sources (the so-called Ma wang dui texts of about the late third century BCE) to the heterogeneous contents of the
1 For further details on the heterogeneous nature of the Huang Di nei jing texts, and a preliminary analysis of historical developments reflected in these texts, see Paul U. Unschuld, Huang Di Nei Jing Su Wen: Nature, Knowledge, Imagery in an Ancient Chinese Medical Text. Berkeley: University of California Press, 2006 (second printing).
Nei jing texts, and, finally, to the homogeneous and highly systematized message of the Nan jing.
Among the Su wen, the Ling shu and the Nan jing, the Su wen is the most difficult one to read. Apparently, at the time of Wang Bing in the ninth century, and according to his introductory remarks to the edition he had prepared, only fragments of the original text were available. The Ling shu, in contrast, is much more homogenous. Presumably, it, too, is a compilation including the thoughts and writings of different ancient authors, arranged by an editor unknown to us, and at a time undefinable today. But the Ling shu is much more systematic than the Su wen, and it has a clear focus: needle therapy, both in the sense of modern acupuncture and in terms of bloodletting. The origin and contents of the Nan jing justify an identification of this work as one of the three classics of the medicine of systematic correspondence in general.
Whether this was intended by its original (unknown) author or whether it is the result of editorial work by later scholars, the Nan jing covers—in an unusually systematic fashion—all aspects of theoretical and practical health care perceivable within the confines of the yin-yang and Five Phases doctrines, as defined by the original medicine of systematic correspondence. I speak here of the “original” medicine of systematic correspondence because later admixtures to this conceptual system—such as the utilization of drugs (far reaching attempts to create a pharmacology of systematic correspondence were not undertaken before the twelfth century CE)2—do not appear in the Nan jing. Such persistent elements of traditional Chinese health care as demonological medicine and religious healing were not taken into consideration either (apparently irreconcilable with the classic concepts of systematic correspondence, a demonology of systematic correspondence was developed only as late as the early Qing dynasty).3
The Nan jing is comprehensive: it addresses questions concerning the location, size, and normal functions of the basic units that constitute the organism; it dis-
2 For a detailed account of efforts undertaken from the twelfth through the fourteenth century to combine the use of pharmaceutical drugs with the concepts of systematic correspondence, see Paul U. Unschuld, Medicine in China: A History of Pharmaceutics, section C.II. Berkeley: University of California Press, 1986. On the developments during the Song era more recently: Asaf Goldschmidt, The Evolution of Chinese Medicine: Song Dynasty, 960–1200. London: Routledge, 2008.
3 From the seventeenth through the early nineteenth century, eminent Chinese physicians discussed the nature and the reality of demonic apparitions. In this context attempts were made to explain such phenomena on the basis of the concepts of systematic correspondence. For a detailed account see Paul U. Unschuld, Medicine in China: A History of Ideas, section 8.2.3. Berkeley: University of California Press, 1985.
cusses the origins and the nature of diseases; it outlines a system of therapeutic needling; and it develops—in great detail—an innovative approach to diagnosis.
Chinese medicine differs from European science in that it appears to be based on what one might call patterned knowledge. Various patterns of knowledge—sometimes overlapping, sometimes antagonistic and mutually exclusive—exist side by side in the literature and probably, in the minds of the people. There have been Chinese authors who, for reasons about which we can only speculate, have rejected some and accepted only a limited number of other very specific patterns. This is true both on the level of macro-patterns (in that some intellectuals objected to demonological knowledge while acknowledging the paradigm of systematic correspondence) and on the level of micro-patterns (in that some proponents of the paradigm of systematic correspondence rejected the Five Phases concepts, which represent one pattern of knowledge within the paradigm of systematic correspondence, while relying solely on the yin-yang doctrine which represents another pattern within that paradigm).
In general, however, a notion seems to have prevailed in China that lent some justification to all patterns of human knowledge. A specific pattern might be useful for handling a certain issue or situation successfully, and it might be contradicted logically by another pattern of knowledge that had also proven to be useful for handling the same (or another) issue. Both patterns—and this seems to have been the dominant attitude in Chinese history—were therefore legitimized. The “either/or” approach that springs to a mind trained in the Western tradition appears to have been posed with much less persistence in Chinese medicine.
Hence authors did not find it difficult to propose, in one and the same book, therapeutic guidelines derived from, as a Western reader might conclude, logically mutually exclusive paradigms or patterns of knowledge. Such “pragmatic” tendencies have been observed in the behavior of patients and practitioners all over the world: wherever two or more conceptual systems of health care coexist, the population is known to oscillate between these systems and utilize them eclectically or syncretically according to its perceived needs. What appears particularly characteristic of China is the fact that this conciliatory attitude toward differing patterns of knowledge is so enormously pervasive. True, heated polemics were exchanged between the proponents of contradictory paradigms, but once a new pattern had existed long enough, its antagonistic relation with older paradigms tended to decrease in importance until it was accepted into the heterogeneous pool of patterns from which a patient or practitioner could select the one most suitable for coping successfully with the specific problem at hand.
Nan
In its outline of diagnosis, the Nan jing itself provides ample evidence of a harmonious coexistence of micro-patterns within the paradigm of systematic correspondence—micro-patterns that have a common theoretical basis but that are, nevertheless, difficult to reconcile with one another. Within his accepted conceptual framework, the author of the Nan jing linked differing patterns of diagnosis without posing the either/or question that is implicit in all Western secondary literature on traditional Chinese medicine. Western authors seem to be continually forced to decide which single pattern of knowledge (whether on the macro- or on the micro-level) they should present to their readers. Almost unanimously, they have not accepted Chinese demonological and religious therapies as facets of traditional or contemporary Chinese medicine, despite the fact that these patterns of knowledge have exerted a tremendous impact on health care in China from remote antiquity up to the most recent times. On a smaller scale, to give another example, the either/or approach demands an answer to whether terms like xin (“heart”), gan (“liver”), and pi (“spleen”) must be understood solely as references to abstract functional systems that do not necessarily correspond to tangible anatomical structures (as some passages in ancient Chinese literature suggest) or as designations of concrete structures within the organism (as other passages suggest). Clearly, both notions have coexisted in traditional Chinese medical literature, so it should be a moot point as to which interpretation of the Chinese terms is correct.
As a consequence of decisions in favor of one or another notion or pattern of knowledge, Western authors writing on traditional Chinese medicine tend to be selective and to omit all patterns of knowledge that fail to correspond to the demands of conceptual coherency or stringency (perhaps this attitude is motivated by an underlying fear that Chinese medicine otherwise might appear “unscientific” to a contemporary audience). In the short run, such a streamlined Chinese medicine may indeed generate the attraction intended by its advocates, especially if it appears clad in Greco-Latin terminology and based on the Western concept of energy. In the long run, however, this does a disservice not only to those who wish to learn about the real nature of Chinese medicine but also to the traditional conciliatory worldview underlying the patterned knowledge of traditional Chinese health care —and to whatever beneficial effects that worldview may still promise to humanity in general.
The present edition of the Nan jing shall point to a different direction. Because it includes not only the entire text itself but also selected commentaries from twenty authors of the third through the twentieth century, the reader will become familiar both with the contents and general history of the reception of this text through the centuries and with differences in opinion voiced by medical authors over time. Con-
sequently, a vivid portrait of an ongoing discussion should emerge which reflects some (and only some) of the dynamics inherent in historical Chinese medicine and which documents some of the strengths and weaknesses of the concepts that underlie the medicine of systematic correspondence.
However, this annotated translation of the Nan jing should serve primarily as a research tool. When its first edition appeared in 1986, I expressed in this preface a hope that the publication of this book might stimulate others to embark on the difficult task of philological analysis of further writings from the history of Chinese medicine, and to develop ever-improving methodologies for conveying the concepts they contain to a Western readership. It is only with the understanding resulting from such analysis that historians, anthropologists, sociologists, and others concerned with the exploration of science and knowledge will have the tools that permit them to pose comparative and other questions. And it is only with this kind of access to the primary sources that those interested in the practice of Chinese medicine as an alternative to Western medicine will be in a position to determine whether the concepts of historical Chinese medicine are indeed applicable to a contemporary Western clientele in any meaningful way.
In concluding the 1986 preface, I pointed out, with sincere gratitude, the unconditional support I received from the China Research Institute for the History of Medicine and Medical Literature at the Academy of Traditional Chinese Medicine in Beijing, where I enjoyed ideal working conditions during two study periods in 1982 and 1983. My special thanks went to Professors Ma Jixing and Ma Kanwen, who found the time to discuss with me a number of problematic passages, and who enabled me to gain access to rare sources unavailable in the United States or Europe. I am happy to know that thirty years later both are still among us. Similar thanks went to the Research Institute for Humanistic Studies of Kyoto University, and especially to Dr. Akira Akahori, who sadly has passed away in the meantime, for his valuable suggestions and for his part in compiling the list of commentated Nan jing editions published by Japanese authors. Financial assistance for conducting this study and traveling to East Asia was provided by a Heisenberg grant and by travel subsidies awarded by the German Research Association (DFG), to whose officers and consultants I am most grateful for the understanding my project received. Finally, my thanks go to the academic editorial board of the Münchener Medizinische Wochenschrift for a grant that assisted in the production of this volume. With the current revised edition I wish to add Dr. Horst Görtz to this list of benefactors. The Horst-Görtz-Institute for the Theory, History, and Ethics of Chinese Life Sciences endowed by him offered me a unique opportunity to continue my philological and historical studies of ancient Chinese medical texts and to complete
Nan Jing - The Classic of
both a new translation of the Nan jing adapted to my changing understanding of the terminology of ancient Chinese medicine, and a first-time annotated philological translation of the Ling shu. With the availability on an identical level of the Su wen, the Ling shu, and the Nan jing to non-Chinese readers, a foundation is laid to compare these texts not only with their contemporary equivalents, such as the ancient Greek Corpus Hippocraticum, but also with the writings of more recent time as vestiges of an ancient knowledge that was most revolutionary from its beginning.
Historical Significance of the Nan jing
The prehistory of the Nan jing as a work marking the apex of the application of the concepts of yin-yang and of the Five Phases to medicine in Chinese antiquity may have begun at some time in the third century BCE with the emergence of the medicine of systematic correspondence. As far as we can judge from the evidence available today, before the third century BCE, health care in China was based on a recognition of an ancestral responsibility in matters of disease and health (a doctrine that seems to have dominated during the Shang and early Zhou), and on an awareness of the activities of malevolent demons as causative agents of human disease.4 In addition, although less well documented, it must be assumed that pharmaceutical drugs played an important role in health care (without necessarily being linked to either demonological or ancestral concepts). Historical sources, such as the Zuo zhuan , contain many references to nonmetaphysical concepts of etiology that allegedly date back as far as the sixth century BCE. Yet whether, for instance, the remarks made by the physician He (when he reproached the Marquis of Jin for his excessive intercourse with women) to the effect that “the six heavenly qi [i.e., yin, yang, wind, rain, obscurity, and brightness] when they are in excess produce the six diseases” do indeed reflect a mode of thinking existing at that time, or whether they constitute a retrospective political metaphor phrased from the perspective of half a millennium later, can hardly be decided as long as no evidence from the era in question has come to light.5
The earliest extant Chinese medical texts are the texts discovered at Ma wang dui . Together with the data in historical and philosophical sources of the last centuries BCE, these texts suggest that, concurrently with the first unification of the Chinese empire between the third and the first centuries BCE, ancestral and
4 Ibid., chapters 1 and 2.
5 See Chun qiu Zuo zhuan , Book X, Duke Chao, First Year.
demonological concepts of health care were supplemented by a conceptual system employing nonmetaphysical notions of natural law.6 This new medicine appears to have been developed as a consequence of the emergence of at least two philosophical schools (with origins traceable to the fifth century BCE) that introduced paradigms of systematic correspondence to China. The doctrines they expounded were based on the yin-yang and Five Phases paradigms. The representatives of the two doctrines opposed each other vehemently in the beginning, and yet in a manner typical of subsequent developments neither was the contradiction between the two doctrines solved in a true synthesis, nor did one paradigm win over the other. Rather, the two were linked (although this proved by no means an easy task). Thereafter, the rise, transformation, and disappearance of any phenomenon in the real world or in the world of concepts could be interpreted by referring to its correspondence to the interactive dynamics of the yin-yang categories of all existence, to the interactive dynamics of the Five Phases of all existence, or to both whichever appeared to be most conclusive.
Throughout its history of two thousand years, the medicine of systematic correspondence has been transformed and expanded. It has even been linked to originally rival paradigms when the Zeitgeist allowed for such bridges. The medicine of systematic correspondence has always been the subject of probing debates among intellectuals and practitioners of historical Chinese medicine; over the centuries, there have been countless attempts at reconciling its basic tenets with thoughts and experience gained by physicians in actual clinical therapy. Yet the formative period of the medicine of systematic correspondence appears to have been marked by extraordinary dynamics within a relatively short span of time dynamics that were unsurpassed even by the developments between the twelfth and fifteenth century.
The medicine of systematic correspondence may be traced from a collection of individual writings of the late third or early second century BCE (unearthed from the tombs at Ma wang dui in the early 1970s), which recommend health care and therapy based on demonology, concepts of magic and systematic correspondence, as well as surgical and pharmaceutical knowledge that may have been derived in part from experience and observation (without theoretical underpinnings).7 From here, it may be traced to the Huang Di nei jing Su wen and Ling shu anthologies of
6 See Unschuld, Medicine in China: A History of Ideas, chapter 3.
7 For a survey of all fourteen medical manuscripts unearthed from the Ma wang dui tombs, see Donald Harper, Early Chinese Medical Literature. The Mawangdui Medical Manuscripts. New York: Routledge, 1997. These manuscripts demonstrate the coexistence of demonological, magic, empirico-pharmaceutical, petty surgical, and further therapeutic concepts and practices in Chinese medicine around 200 BCE.
Jing - The Classic of
systematic correspondence of the second or first century BCE, in which only a few allusions to demonology and drug lore remain, and thence to its conclusion that is, to the compilation of the Nan jing around the first century CE.
This early phase of development included the struggle between the yin-yang and Five Phases doctrines and their convergence in the field of medicine; the transition of the concept of “wind” from a spirit entity to a non-metaphysical natural phenomenon responsible for disease; and the partial replacement of the concept of “wind” by a concept of “vapors” (qi ) that underlie all physiological and pathological change. This phase also included an innovative understanding of the functional structure of the organism and the introduction of a therapeutic technique hitherto unknown (or at least undocumented) in China namely, needling or acupuncture.
The significance of the Nan jing in this historical context is twofold. First, its unknown author contributed to the formative period of the medicine of systematic correspondence by creating a conceptual system of medical theory and practice that for the first time consistently accounted for the “discovery” of a circulatory movement in the organism (documented earlier in the Huang Di nei jing texts).8 Second, the Nan jing marks the end of this formative epoch because it discarded all the irrelevant ballast of the past and concentrated in a most coherent manner on nothing but the most advanced concepts of systematic correspondence. No similar work has since been written.
In devising his conceptual system, the author of the Nan jing adopted, with no change, a number of concepts from the Huang Di nei jing texts. In addition, he borrowed some older terms but adapted them to his own ideas by presenting them with a modified meaning. Finally, he introduced a series of innovative terms and concepts to complete the doctrine he intended to teach.
The core idea around which the entire Nan jing appears to be centered is a modification of diagnosis and therapy in accordance with the “discovery” of a circulatory movement of qi (and blood) in the organism a discovery that may have occurred some time during the second century BCE.9 Two of the Mawangdui manuscripts
8 See, for instance, Su wen treatise 39, “Ju tong lun” .
9 Lu and Needham (Celestial Lancets, Cambridge, 1980, 23) have suggested an even earlier emergence of a concept of physiological circulation in China. As evidence they quoted a passage from the Guanzi (identified by Lu and Needham as a text from the fourth century BCE): shui zhe di zhi xue qi ru jin mai zhi tong liu zhe ye . In Lu’s and Needham’s translation this passage reads: “[One can say that] water is the blood and the chhi of the earth, because it flows and penetrates everywhere [just in the same manner] as the circulation [of the chhi and the blood] in the ching-chin [nerve, muscle and tendon] and the ching-mo [tract and channel, including blood vessel] systems.” Rendered literally, this passage reads: “Water is the blood and the qi of the earth; it flows and penetrates everywhere just as the sinews and the vessels.” One might
of around 200 BCE (i.e., the Shi yi mai jiu jing texts) refer to eleven vessels that permeate separately and without mutual interconnection the human body. Six of these vessels extend upward from the feet into abdomen and chest (some of them reaching the head); five are described as extending from the hands into the chest or head. These vessels are filled with qi vapors; they may suffer from depletion or repletion, or from unusual movements of their contents.
Each of these vessels has its own diseases that produce characteristic symptoms. The sole treatment recommended for manipulating the contents of the eleven vessels is heat, applied by burning a particular herbal substance on the courses the afflicted vessels are believed to take. No specific points at which to conduct such treatment are identified.
By the time those sections of the Huang Di nei jing texts that are concerned with physiology and needling were compiled, significant changes had taken place. Twelve vessels were named, which take different courses in comparison to the eleven vessels of the Mawangdui scripts, and which form an interconnected system of “streams” or “conduits” (jing ) that extends throughout the body. The circuit of these conduits represented the central structure of a fine net of passageways formed—in addition to the main conduits—by so-called network vessels (luo mai ) and “tertiary vessels” (sun mai ).
Through these conduits, an endless flow of qi was believed to pass, partially taken in from the outside environment and partially generated by the organism itself. Each of the vessels was known to correspond to one of the basic functional units in the body, and to signal—through changes occurring in the movement inside it—diseases affecting the corresponding unit. The movement in the vessels caused the vessels themselves to pulsate in a particular way. Points were defined all over the body where the individual conduit vessels could be palpated to assess, through the condition of their movement, the condition of the functional units with which they were associated.
For treatment, the Huang Di nei jing recommended primarily the insertion of needles at specific locations on all twelve conduit vessels. Since needling was first mentioned in China in the Shi ji of 90 BCE, and since it obviously was not known to the authors of the manuscripts unearthed from the Ma wang dui tombs go a little further and accept the following interpretation: “Water is the blood and the qi of the earth; it flows and penetrates everywhere just as [the blood and the qi in] the sinews and vessels [of the human body].” Guanzi appears to refer here to a physiological concept reflecting the image of waterways and their contents (above and below the surface of the earth) permeating the entire country. The Chinese wording suggests neither a physiological concept of circulation nor a “meteorological water cycle.” For further details on the origin of the circulation concept in Chinese medicine, see Unschuld, Medicine in China: A History of Ideas, chapter 3.3.2.
(who recorded every other possible mode of treatment), we may assume that the acupuncture sections of the Nei jing were conceptualized and compiled not earlier than during the late second or first century BCE.10
The author of the Nan jing may have recognized a contradiction between the notion of an ongoing circulatory movement in the vessels and the idea that each vessel has to be diagnosed and treated as if it constituted an individual entity. If the qi pass through an endless circle of conduits again and again, as the text repeatedly states, “like in a ring without end”, it is difficult to imagine that the quality of their movement changes when they leave one section of the circuit to enter the next. Hence it is almost irrelevant where the movement is examined: one point on the circuit should reveal all the information needed.
Consequently, the author of the Nan jing discarded all locations on the body hitherto used for palpating the vessels, with the exception of one (or, under certain circumstances, two). A problem arose from this concentration—that is, how could one gain from a single point the same information on the condition of the individual functional units of the organism that had been gathered previously from locations spread all over the body?
The information needed to assess a patient’s health and to devise and conduct a proper treatment on the basis of the concepts of systematic correspondence was quite complex. It is one of the merits of the author of the Nan jing that he developed adequately sophisticated diagnostic patterns by linking some forty-seven perceivable types of movement in the conduit vessels (palpable in various surface or vertical sections at the wrist of one or both hands) to all the normal and abnormal states known to affect the functional units of the organism in the course of the annual seasons. All these patterns were, of course, grounded in the concepts of systematic correspondence.
In devising his system of therapy, the author of the Nan jing may have started from conclusions similar to those upon which he based his diagnostic system. Why pierce the individual sections of the circuit through holes scattered all over that circuit if the qi passing through the sections are one and the same? Hence it should be no surprise that the Nan jing does not mention conventional circuit-needling at all, but recommends, first, the needling of “accumulation holes” on the back and front of a patient where certain undesired qi gather and can be removed. Second, the Nan jing outlines what we may call “limbs needling,” a scheme previously documented in the Ling shu. In this scheme, twelve streams (running from hands or feet to elbows or knees, respectively) are conceptualized, with five (or six) holes on each. These
10 For a more detailed discussion of the earliest references to needling therapy in Chinese literary sources, see Unschuld, Medicine in China: A History of Ideas, chapter 3.3.4.
streams (jing ) are associated with the basic functional units of the organism, but they are not seen as part of a circuit. Through inserting needles into the holes (bearing such telling names as “well,” “creek,” “rapids/transportation,” “stream,” and “confluence”), it is possible, according to the Nan jing, to influence the organism’s basic functional units in any way desired.
The Contents of the Nan jing
An innovative diagnostic approach and a coherent concept of needling therapy are, on first glance, the two central messages conveyed by the Nan jing; they represent, however, only two ingredients of a virtually complete conceptual system of medical care that also includes a detailed discussion of physiology, etiology, and pathology.
As is the case with the editions of the Su wen and the Ling shu that are extant, the textus receptus of the Nan jing consists of eighty-one sections. In the Su wen, all eighty-one sections are designated by a specific topic to which is added consistently the term lun (“discussion” or simply “on ...”); in the Ling shu, only a fraction of the eighty-one section titles carries the adjunct lun, while the majority have only the topic discussed as their title. In the Nan jing, in contrast, all eightyone sections are merely called nan , and they are numbered consecutively with no topics appearing as titles. The term nan has been interpreted by Eastern and Western authors in various ways. Xu Dachun , an eminent eighteenth century author of conservative medical writings and a commentator on the Nan jing, read nan as “question-and-answer dialogue” or “examination.” He concluded: “The aim [of the Nan jing] is to explain difficult issues in the text of the classic. Hence it poses questions concerning these difficult issues (wen nan ) and, then, clarifies them. Therefore it is called Nan jing.”11 Okanishi Tameto , the late Japanese historian of Chinese medical literature, followed Xu Dachun here when he identified nan as wennan, 12 and so, most recently, did Gu Weicheng , the editor of San bai zhong yi ji lu . 13
Rather than emphasizing the question-and-answer structure of the Nan jing, other authors have understood nan as referring to the “difficult” nature of the issues discussed. Li Jiong , a thirteenth century author of a commentated Nan jing
11 Xu Dachun, “Nan jing lun” , Yi xue yuan liu lun , in Xu Lingtai yi shu quan ji . Taipei. 1969, 113.
13 Gu Weicheng , San bai zhong yi ji lu Harbin, 1982. 25.
Nan Jing - The Classic of Difficult Issues
edition, wrote in his preface that the Nan jing“was structured as a fictitious dialogue in order to elucidate doubtful and difficult meanings. In all, it consists of eighty-one sections. Hence it is called the ‘Classic of Eighty-One Difficult Issues’.”14
A third noteworthy explanation of the title was offered by Itō Kaoru , author of a thoughtful etymological Nan jing commentary (which was never published; his original manuscript is in the Fujikawa Library of Kyoto University). Itō may have had in mind the title of section twelve of Han fei zi (“Shuo nan” ) when he stated: “The meaning of the character nan is that of shuo [here ‘to instruct’, ‘to persuade’] as in shuo nan [‘the difficulties of persuasion’].15 It was used in antiquity to express the meaning of ‘instruction’. It is, therefore, quite appropriate to consider [the wording] ba shi yi nan as carrying the meaning ba shi yi shuo [‘eighty-one instructions’].”16
Over the centuries, various schemes have been introduced to group the eightyone difficult issues. Allegedly dating back to the Tang commentator Yang Xuancao (eighth century) is a system of thirteen chapters that was repeated by the Nan jing ji zhu edition of the early sixteenth century.17 Other editions followed a classification initiated by Wu Cheng (1247-1331), a literatus who grouped the eighty-one difficult issues into only six chapters.18 These two approaches to dividing the eighty-one sections of the Nan jing into meaningful groups or related subjects adopted an identical order of the individual difficult issues. Yet a few commentators, especially those of more recent times, have felt the need to rearrange—and even cut apart—a number of difficult issues to recombine segments
14 Taki Mototane , Zhong guo yi ji kao Peking, 1956. 45.
15 See Shi ji , ch. 63.
16 Ito Kaoru, Nan jing wenzi kao, n.d., n.p. (see appendix C).
17 See Yang’s preface reprinted in Okanishi Tameto, Song yi qian yi ji kao (Taipei, 1969), 107. The thirteen chapters adopted by the Nan jing ji zhu edition are: 1. Diagnosing the [movement in the] conduit vessels (sections 1–24); 2. Enumeration of [main] conduits and network [vessels] (sections 25 and 26); 3. The eight single-conduit vessels (sections 27–29); 4. camp and guard [qi] and the Triple Burner (sections 30 and 31); 5. The long-term depots and the short-term repositories and their correspondences (sections 32–37); 6. Enumeration and measurements of the long-term depots and short-term repositories (sections 38–47); 7. Depletion, repletion, evil [qi], and proper [qi] (sections 48–52); 8. Transmission of diseases through long-term depots and short-term repositories (sections 53 and 54); 9. Accumulation and collection [illnesses] in the long-term depots and short-term repositories (sections 55 and 56); 10. The five diarrheas and harm caused by cold (sections 57–60); 11. Spirits, sages, artisans, and workmen (section 61); 12. Wells [and other] transportation holes [associated with the] long-term depots and short-term repositories (sections 62–68); 13. upplementing and draining with needles (sections, 69–81).
18 Okanishi Tameto 1974, 15.
Prolegomena
of the text they interpreted as originally belonging together.19 And concurrent with contemporary attempts to filter out of the entirety of traditional Chinese medicine those elements that some authors consider worth preserving and utilizing in practice, a few editions have been published recently which—in contrast to all former editions (which included even those sections of the Nan jing considered to be wrong or absurd)—present not the complete text but only selected passages.20 In the present edition of the complete text, the eighty-one difficult issues are presented in the traditional order adopted by all the pre-eighteenth-century editions I have seen. Since the original division of the text into “chapters” prior to Yang Xuancao—if there was one—is no longer known, I have adopted the six-chapter scheme introduced by Wu Cheng for its conciseness and clarity.
The following is a survey of the contents of each of the eighty-one difficult issues grouped in six chapters.
Chapter One: The Movement in the Vessels and its Diagnostic Significance
The first difficult issue
Explanation of the significance of the inch opening for diagnosing diseases through investigating the movement in the vessels.
The second difficult issue
Introduction of the first subdivision of the inch opening into an “inch section” and a “foot section,” divided by a line called “gate.”
The third difficult issue
Discussion of the terms “great excess,” “insufficiency,” “mutual takeover by yin and yang,” “turnover,” “overflow,” “closure,” and “barrier” as diagnostic parameters indicated by specific movements in the vessels.
The fourth difficult issue
Explanation of yin and yang patterns of movement in the vessels, and introduction of the concept of three longitudinal levels in the movement in the vessels.
The fifth difficult issue
Introduction of the concept of five longitudinal levels in the movement in the vessels, and of a method to distinguish these levels.
The sixth difficult issue
19 For instance, Katō Bankei in his Nan jing gu yi of 1784 (see appendix B) and Huang Weisan in his Nan jing zhi yao of 1967 (see appendix A). See also He Aihua, “Guan yu Nan jing de bian ci wen ti,” Ha er bin zhong yi 8 (1965): 41–43 (see appendix B).
20 For instance, Yan Hongchen and Gao Guangzhen in their Nei Nan jing xuan shi of 1979 (see appendix A).
Discussion of the terms “yin abundance, yang depletion” and “yang abundance, yin depletion” as diagnostic parameters indicated by specific movements in the vessels.
The seventh difficult issue
Explanation of the significance of the appearance of any of the three yin and three yang kinds of movement in the vessels as they are related to the six periods within one year.
The eighth difficult issue
Explanation of the significance of the “moving qi” (also called “vital qi”) in the organism, as appearing at the inch opening.
The ninth difficult issue
How to distinguish diseases in the long-term depots and short-term repositories by the speed of the movement in the vessels.
The tenth difficult issue
Introduction of the concept of “ten variations” in the movement in the vessels, as can be felt in the different sections at the wrist that are associated with specific long-term depots.
The eleventh difficult issue
Explanation of the concept that one long-term depot is void of qi if the movement in the vessels stops once in less than fifty arrivals.
The twelfth difficult issue
Introduction of the concept that the internal or external parts of the organism may be cut off from the movement in the vessels.
The thirteenth difficult issue
Introduction of the concept of a correspondence between a person’s complexion, the movement in the vessels as felt at the inch opening, and the condition of the skin in the foot section of the lower arm.
The fourteenth difficult issue
Introduction of the concepts of “injured” (i.e., slower than usual) and “arriving” (i.e., faster than usual) movements in the vessels; also, discussion of the significance of the presence of a movement in the vessels at the inch section when no movement can be perceived at the foot section, and vice versa.
The fifteenth difficult issue
Elucidation of the changes in the movements in the vessels in accordance with the passing of the four seasons.
The sixteenth difficult issue
Prolegomena
Discussion of various methods to diagnose diseases by taking internal and external evidence into account.
The seventeenth difficult issue
How to predict a patient’s impending death or survival by comparing the movement in his vessels with other manifestations of his disease.
The eighteenth difficult issue
Systematized presentation of the correspondences of the yin and yang conduits with the inch, gate, and foot sections near the wrist where the movement in the vessels can be felt, on the basis of the mutual generation order of the Five Phases. Also, discussion of methods for recognizing internal accumulations and chronic diseases through the movement in the vessels.
The nineteenth difficult issue
Introduction of the concept of differences in the movement in the vessels in males and females.
The twentieth difficult issue
Introduction of the concepts of hidden and concealed movements in the vessels, of doubled qi, and of lost qi.
The twenty-first difficult issue
On the prognostic significance of situations where a patient’s bodily appearance shows signs of disease while the movement in his vessels does not, and vice versa.
The twenty-second difficult issue
Elaboration of the concepts of diseases in the vessels that are “excited” and of those that are “generated.”
Chapter Two: The Conduits and the Network Vessels
The twenty-third difficult issue
Systematized presentation of the lengths and courses of the conduit vessels as sections of a large circulatory system. Also, reference to the significance of feeling the movement in the vessels at the wrists of both hands, and explanation of the concepts of “end” and “beginning.”
The twenty-fourth difficult issue
Systematized presentation and prognostic evaluation of external symptoms indicating that a specific conduit vessel has been cut off from the movement in the vessels.
The twenty-fifth difficult issue
Explanation of the concept of “twelve conduits” in the presence of five long-term depots and six short-term repositories through the introduction of the concepts of “heart enclosing network” and “Triple Burner” as carrying a name (i.e., fulfilling a function) without having a form (i.e., an anatomical substratum).
The twenty-sixth difficult issue
Remarks on the fifteen network vessels.
The twenty-seventh difficult issue
Introduction of the term “eight single-conduit vessels,” and of the concept that they function as “ditches and reservoirs” absorbing surplus contents of the main conduits.
The twenty-eighth difficult issue
Description of the courses of the eight single-conduit vessels in the organism.
The twenty-ninth difficult issue
List of signs and symptoms caused by diseases in the eight single-conduit vessels.
Chapter Three: The Long-Term Depots and the Short-Term Repositories
The thirtieth difficult issue
Elucidation of the concepts of camp qi and guard qi, and introduction of the idea that the long-term depots and short-term repositories are supplied with qi by the stomach directly.
The thirty-first difficult issue
Innovative reinterpretation of the concept of the Triple Burner as a functional description of the upper, central, and lower groups of organs in the body.
The thirty-second difficult issue
Explanation of why the heart and the lung are the only long-term depots located above the diaphragm.
The thirty-third difficult issue
Discussion of apparent contradictions resulting from the association of the liver and kidneys with the phases wood and metal, respectively.
The thirty-fourth difficult issue
Pattern of the five long-term depots and their corresponding sounds, complexions, odors, liquids, and flavors. Association of the five long-term depots with the seven spirits.
The thirty-fifth difficult issue
Prolegomena
Discussion of theoretical issues concerning the functions and locations of the six short-term repositories, especially as they are related to the five long-term depots.
The thirty-sixth difficult issue
Introduction of the concept that the organism has two kidneys, one of them constituting the “gate of life.”
The thirty-seventh difficult issue
Elucidation of the concept that the qi of the five long-term depots pass through specific orifices, thus maintaining the functions of these orifices. Also, further discussion of the concepts of closure and barrier, and reference to the concepts of turnover and overflow.
The thirty-eighth difficult issue
Further elucidation of the nature and function of the Triple Burner as an answer to the question of why there are six short-term repositories but only five longterm depots in the body.
The thirty-ninth difficult issue
Further elucidation of the nature and function of the gate of life and of the Triple Burner in reference to the existence of six short-term repositories but only five long-term depots.
The fortieth difficult issue
Discussion of apparent contradictions resulting from the association of the nose with the lung (which is responsible for the sounds, while the nose is responsible for distinguishing the odors) and from the association of the ears with the kidneys (which are responsible for the liquids, while the ears are responsible for distinguishing the sounds).
The forty-first difficult issue
Explanation of why the liver is the only long-term depot that has two lobes.
The forty-second difficult issue
Description of all long-term depots and short-term repositories in terms of length, diameter, weight, and capacity.
The forty-third difficult issue
Explanation of the phenomenon that someone who does not eat or drink will die after seven days.
The forty-fourth difficult issue
List of the names and locations of the seven through-gates.
The forty-fifth difficult issue
Introduction of the concept of the eight gathering points.
The forty-sixth difficult issue
On different sleeping patterns in old and young people.
The forty-seventh difficult issue
Why the face can stand cold.
Chapter Four: On diseases
The forty-eighth difficult issue
Introduction of various diagnostic patterns allowing one to distinguish whether a person suffers from a depletion or from a repletion.
The forty-ninth difficult issue
Introduction of the concepts of primary affection by the five evil qi from outside the organism, and of secondary affection by evil qi transmitted within the organism.
The fiftieth difficult issue
Introduction of the concepts of “depletion evil,” “repletion evil,” “robber evil,” “weakness evil,” and “regular evil,” denoting the five possibilities of internal secondary affliction.
The fifty-first difficult issue
Explanation of different preferences and aversions on the side of the patient permitting one to distinguish whether a disease is located in the long-term depots or short-term repositories.
The fifty-second difficult issue
On the static nature of diseases in the long-term depots and on the mobile nature of diseases in the short-term repositories.
The fifty-third difficult issue
Introduction of the concepts of “transmission of a disease through seven longterm depots” and of “transmission skipping a depot.”
The fifty-fourth difficult issue
Diseases in the long-term depots are difficult to cure; diseases in the short-term repositories are easy to cure.
The fifty-fifth difficult issue
Reinterpretation of the concepts of “accumulation” and “collection” diseases.
The fifty-sixth difficult issue
Prolegomena
Reinterpretation of terms and concepts related to accumulation diseases, and introduction of a systematic theory of the generation of the five accumulation diseases.
The fifty-seventh difficult issue
Introduction of a fivefold classification of different diarrheas.
The fifty-eighth difficult issue
Introduction of a fivefold classification of “harm caused by cold” diseases and of the different movements in the vessels resulting from these diseases. Also, a list of signs and symptoms allowing for a diagnosis of diseases caused by heat and cold.
The fifty-ninth difficult issue
How to distinguish peak-illness from madness.
The sixtieth difficult issue
Discussion of the concepts of “stagnant pain” and “true pain” in head and heart.
The sixty-first difficult issue
Introduction of a categorization of healers as “spirits,” “sages,” “artisans,” and “workmen,” based on their respective approaches to diagnosing a disease.
Chapter Five: Transportation Holes
The sixty-second difficult issue
Explanation of why the conduits associated with the short-term repositories have six transportation holes, while those associated with the long-term depots have only five.
The sixty-third difficult issue
Explanation of why each conduit has a “spring” as its first transportation hole.
The sixty-fourth difficult issue
Introduction of a systematic categorization of the transportation holes according to yin and yang and the Five Phases.
The sixty-fifth difficult issue
Remarks concerning the “spring” and “confluence” transportation holes.
The sixty-sixth difficult issue
Discussion of the “origin” transportation holes as outlets of the “original qi” of the six long-term depots and six short-term repositories.
The sixty-seventh difficult issue
Explanation of the location of “levy holes” on the front and of “transportation holes” on the back of one’s body.
The sixty-eighth difficult issue
Introduction of a list of diseases that can be cured by needling the respective transportation holes associated with them.
Chapter Six: Needling Patterns
The sixty-ninth difficult issue
General advice on how to supplement a depletion and drain a repletion, and when to remove a disease from an affected conduit itself.
The seventieth difficult issue
Introduction of a pattern of two different needling techniques to be applied during the spring-summer and autumn-winter seasons, respectively.
The seventy-first difficult issue
Advice for needling the camp qi and the guard qi.
The seventy-second difficult issue
Reinterpretation of the terms “moving against” and “following” as concepts referring to the direction of the movement in the vessels.
The seventy-third difficult issue
Advice to needle a “creek” transportation hole if theory requires needling a “well” hole.
The seventy-fourth difficult issue
Introduction of a pattern of needling different holes in the course of the five seasons.
The seventy-fifth difficult issue
Elucidation of the theoretical basis underlying the therapeutic approach of supplementing a so-called depletion and of draining a so-called repletion.
The seventy-sixth difficult issue
Discussion of the concepts of “supplementing” and “draining.”
The seventy-seventh difficult issue
Introduction of a classification of healers as “superior” or “mediocre” practitioners according to their understanding of the transmission of diseases within the organism.
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occupies its place. A great deal of ingenuity is displayed by the Parisian artists in the composition of these pictures, and the exhibition of them, either in small portable instruments held in the hand, or placed on the table, or on a great scale, to an audience, by means of the oxygen and hydrogen light, never fails to excite admiration.
The pictures thus exhibited, though finely executed, have only that degree of relief which I have called monocular, and which depends on correct shading and perspective; but when the dissolving views are obtained from binocular pictures, and have all the high relief given them by their stereoscopic combination, the effect must be singularly fine.
Very interesting and amusing effects are produced by interchanging the right and the left eye pictures in the stereoscope. In general, what was formerly convex is now concave, what was round is hollow, and what was near is distant. The effect of this interchange is finely seen in the symmetrical diagrams, consisting of white lines upon black ground, such as Nos. 1, 5, 9, 12, 18 and 27 of the Parisian set; but when the diagrams are not symmetrical, that is, when the one half is not the reflected image of the other, such as Nos. 26, &c., which are transparent polygonal solids, formed as it were by white threads or wires, no effect, beyond a slight fluttering, is perceived. As the right and left eye pictures are inseparable when on glass or silver plate, the experiments must be made by cutting in two the slides on Bristol board. This, however, is unnecessary when we have the power of uniting the two pictures by the convergency of the optic axes to a nearer point, as we obtain, in this case, the same effect as if we had interchanged the pictures. The following are some of the results obtained in this manner from well-known slides:—
In single portraits no effect is produced by the interchange of the right and left eye pictures. If any loose part of the dress is in the foreground it may be carried into the distance, and vice versa. In one portrait, the end of the hat-band, which hung down loosely behind the party, was made to hang in front of it.
In pictures of streets or valleys, and other objects in which the foreground is connected with the middle-ground, and the middleground with the distance, without any break, no effect is produced by the interchange. Sometimes there is a little bulging out of the middle distance, injurious to the monocular effect.
In the binocular picture of the Bridge of Handeck, the Chalet in the foreground retires, and the middle distance above it advances.
In the picture of the sacristy of Notre Dame, the sacristy retires within the cathedral.
In the Maison des Chapiteaux at Pompeii, the picture is completely inverted, the objects in the distance coming into the foreground.
In the Daguerreotype of the Crystal Palace, the water in the foreground, with the floating plants, retires and takes an inclined position below a horizontal plane.
In the binocular picture of the lower glacier of Rosenlaui, the roof of the ice-cave becomes hollow, and the whole foreground is thrown into a disordered perspective.
In Copeland’s Venus, the arm holding the bunch of grapes is curiously bent and thrown behind the head, while the left arm advances before the child.
In the picture of the Greek Court in the Crystal Palace, the wall behind the statues and columns advances in front of them.
The singular fallacy in vision which thus takes place is best seen in a picture where a number of separate articles are placed upon a table, and in other cases where the judgment of the spectator is not called upon to resist the optical effect. Although the nose of the human face should retire behind the ears yet no such effect is produced, as all the features of the face are connected with each other, but if the nose and ears had been represented separately in the position which they occupy in the human head, the nearer features would have retired behind the more remote ones, like the separate articles on a table.
We shall have occasion to resume this subject in our concluding chapter on the fallacies which take place in viewing solids, whether raised or hollow, and whether seen by direct or inverted vision.
CHAPTER XV. ON THE PRODUCTION OF STEREOSCOPIC PICTURES
FROM A SINGLE PICTURE.
Those who are desirous of having stereoscopic relievos of absent or deceased friends, and who possess single photographic portraits of them, or even oil paintings or miniatures, will be anxious to know whether or not it is possible to obtain from one plane picture another which could be combined with it in the stereoscope; that is, if we consider the picture as one seen by either eye alone, can we by any process obtain a second picture as seen by the other eye? We have no hesitation in saying that it is impossible to do this by any direct process.
Every picture, whether taken photographically or by the eye, is necessarily a picture seen by one eye, or from one point of sight; and, therefore, a skilful artist, who fully understands the principle of the stereoscope, might make a copy of any picture as seen by the other eye, so approximately correct as to appear in relief when united with the original in the stereoscope; but the task would be a very difficult one, and if well executed, so as to give a relievo without distortion, the fortune of the painter would be made.
When the artist executes a portrait, he does it from one point of sight, which we may suppose fixed, and corresponding with that which is seen with his left eye. If he takes another portrait of the same person, occupying exactly the same position, from another point of sight, two and a half inches to the right of himself, as seen with his right eye, the two pictures will differ only in this, that each point in the head, and bust, and drapery, will, in the second picture, be carried farther to the left of the artist on the plane of
representation. The points which project most, or are most distant from that plane, will be carried farther to the left than those which project less, the extent to which they are carried being proportional to the amount of their projection, or their distance from the plane. But since the painter cannot discover from the original or left-eye plane picture the degree of prominence of the leading points of the head, the bust, and the drapery, he must work by guess, and submit his empirical touches, step by step, to the judgment of the stereoscope. In devoting himself to this branch of the art he will doubtless acquire much knowledge and dexterity from experience, and may succeed to a very considerable extent in obtaining pictures in relief, if he follows certain rules, which we shall endeavour to explain.
If the given portrait, or picture of any kind, is not of the proper size for the stereoscope, it must be reduced to that size, by taking a photographic copy of it, from which the right-eye picture is to be drawn.
F . 50.
In order to diminish the size of the diagram, let us suppose that the plane on which the portrait is taken touches the back of the head, and is represented in section by , Fig. 50. We must now assume, under the guidance of the original, a certain form of the head, whose breadth from ear to ear is ″, being the point of the nose in the horizontal section of the head, ″ ′, passing through the nose , and the lobes ″ of the two ears. Let , be the left and right eyes of the person viewing them, and the distance at which they are viewed, and let lines be drawn from and , through , , and ″, meeting the plane on which the portrait is taken in e′, ‴, n, ′, e,
and ′ The breadth, ‴e′, and the distances of the nose from the ears ′ ′, ′ ‴, being given by measurement of the photograph suited to the stereoscope, the distances ′, ′, ″ ‴ may be approximately obtained from the known form of the human head, either by projection or calculation. With these data, procured as correctly as we can, we shall, from the position of the nose n, as seen by the right eye , have the formula
′n = × ′ .
The distance of the right ear e′, from the right-eye picture, will be, ne′ = e′ - ′n; and as ′e = × ′ .
The distance of the left ear e, in the right-eye picture, from the nose n, will be ne = ′n + ′ ′ - ′e.
In order to simplify the diagram we have made the original, or lefteye picture, a front view, in which the nose is in the middle of the face, and the line joining the ears parallel to the plane of the picture.
When the position of the nose and the ears has been thus approximately obtained, the artist may, in like manner, determine the place of the pupils of the two eyes, the point of the chin, the summit of the eyebrows, the prominence of the lips, and the junction of the nose with the teeth, by assuming, under the guidance of the original picture, the distance of these different parts from the plane of projection. In the same way other leading points in the figure and drapery may be found, and if these points are determined with tolerable accuracy the artist will be able to draw the features in their new place with such correctness as to give a good result in the stereoscope.
In drawing the right-eye picture the artist will, of course, employ as the groundwork of it a faint photographic impression of the original, or left-eye picture, and he may, perhaps, derive some advantage from placing the original, when before the camera, at such an inclination to the axis of the lens as will produce the same diminution in the horizontal distance between any two points in the head, at a mean distance between and ′, as projected upon the plane . The line ′ ‴, for example, which in the left-eye photograph is a representation of the cheek ″, is reduced, in the right-eye photograph, to ne′, and, therefore, if the photograph on , as seen by the right eye, were placed so obliquely to the axis of the lens that ′e was reduced to ne′, the copy obtained in the camera would have an approximate resemblance to the right-eye picture required, and might be a better groundwork for the right-eye picture than an accurate copy of the photograph on , taken when it is perpendicular to the axis of the lens.
In preparing the right-eye picture, the artist, in place of using paint, might use very dilute solutions of aceto-nitrate of silver, beginning with the faintest tint, and darkening these with light till he obtained the desired effect, and, when necessary, diminishing the shades with solutions of the hypo-sulphite of soda. When the picture is finished, and found satisfactory, after examining its relief in the stereoscope, a negative picture of it should be obtained in the camera, and positive copies taken, to form, with the original photographs, the pair of binocular portraits required.
CHAPTER XVI. ON CERTAIN FALLACIES OF SIGHT
IN THE VISION OF SOLID BODIES.
In a preceding chapter I have explained a remarkable fallacy of sight which takes place in the stereoscope when we interchange the binocular pictures, that is, when we place the right-eye picture on the left side, and the left-eye picture on the right side. The objects in the foreground of the picture are thus thrown into the background, and, vice versa, the same effect, as we have seen, takes place when we unite the binocular pictures, in their usual position, by the ocular stereoscope, that is, by converging the optic axes to a point between the eye and the pictures. In both these cases the objects are only the plane representations of solid bodies, and the change which is produced by their union is not in their form but in their position. In certain cases, however, when the object is of some magnitude in the picture, the form is also changed in consequence of the inverse position of its parts. That is, the drawings of objects that are naturally convex will appear concave, and those which are naturally concave will appear convex.
In these phenomena there is no mental illusion in their production. The two similar points in each picture, if they are nearer to one another than other two similar points, must, in conformity with the laws of vision, appear nearer the eye when combined in the common stereoscope. When this change of place and form does not appear, as in the case of the human figure, previously explained, it is by a mental illusion that the law of vision is controlled.
The phenomena which we are about to describe are, in several respects, different from those to which we have referred. They are seen in monocular as well as in binocular vision, and they are produced in all cases under a mental illusion, arising either from
causes over which we have no control, or voluntarily created and maintained by the observer. The first notice of this class of optical illusion was given by Aguilonius in his work on optics, to which we have already had occasion to refer.[69] After proving that convex and concave surfaces appear plane when seen at a considerable distance, he shews that the same surfaces, when seen at a moderate distance, frequently appear what he calls converse, that is, the concave convex, and the convex concave. This conversion of forms, he says, is often seen in the globes or balls which are fixed on the walls of fortifications, and he ascribes the phenomena to the circumstance of the mind being imposed upon from not knowing in what direction the light falls upon the body. He states that a concavity differs from a convexity only in this respect, that if the shadow is on the same side as that from which the light comes it is a concavity, and if it is on the opposite side, it is a convexity. Aguilonius observes also, that in pictures imitating nature, a similar mistake is committed as to the form of surfaces. He supposes that a circle is drawn upon a table and shaded on one side so as to represent a convex or a concave surface. When this shaded circle is seen at a great distance, it appears a plane surface, notwithstanding the shadow on one side of it; but when we view it at a short distance, and suppose the light to come from the same side of it as the part not in shadow, the plane circle will appear to be a convexity, and if we suppose the light to come from the same side as the shaded part, the circle will appear to be a concavity.
More than half a century after the time of Aguilonius, a member of the Royal Society of London, at one of the meetings of that body, when looking at a guinea through a compound microscope which inverted the object, was surprised to see the head upon the coin depressed, while other members were not subject to this illusion.
Dr. Philip Gmelin[70] of Wurtemberg, having learned from a friend, that when a common seal is viewed through a compound microscope, the depressed part of the seal appeared elevated, and the elevated part depressed, obtained the same result, and found, as Aguilonius did, that the effect was owing to the inversion of the shadow by the microscope. One person often saw the phenomena
and another did not, and no effect was produced when a raised object was so placed between two windows as to be illuminated on all sides.
In 1780 Mr. Rittenhouse, an American writer, repeated these experiments with an inverting eye-tube, consisting of two lenses placed at a distance greater than the sum of their focal lengths, and he found that when a reflected light was thrown on a cavity, in a direction opposite to that of the light which came from his window, the cavity was raised into an elevation by looking through a tube without any lens. In this experiment the shadow was inverted, just as if he had looked through his inverting eye-tube.
In studying this subject I observed a number of singular phenomena, which I have described in my Letters on Natural Magic, [71] but as they were not seen by binocular vision I shall mention only some of the more important facts. If we take one of the intaglio moulds used by the late Mr. Henning for his bas-reliefs, and direct the eye to it steadily, without noticing surrounding objects, we may distinctly see it as a bas-relief. After a little practice I have succeeded in raising a complete hollow mask of the human face, the size of life, into a projecting head. This result is very surprising to those who succeed in the experiment, and it will no doubt be regarded by the sculptor who can use it as an auxiliary in his art.
Till within the last few years, no phenomenon of this kind, either as seen with one or with two eyes, had been noticed by the casual observer. Philosophers alone had been subject to the illusion, or had subjected others to its influence. The following case, however, which occurred to Lady Georgiana Wolff, possesses much interest, as it could not possibly have been produced by any voluntary effort. “Lady Georgiana,” says Dr Joseph Wolff in his Journal, “observed a curious optical deception in the sand, about the middle of the day, when the sun was strong: all the foot-prints, and other marks that are indented in the sand, had the appearance of being raised out of it. At these times there was such a glare, that it was unpleasant for the eye.”[72] Having no doubt of the correctness of this observation, I have often endeavoured, though in vain, to witness so remarkable a
phenomenon. In walking, however, in the month of March last, with a friend on the beach at St. Andrews, the phenomenon presented itself, at the same instant, to myself and to a lady who was unacquainted with this class of illusions. The impressions of the feet of men and of horses were distinctly raised out of the sand. In a short time they resumed their hollow form, but at different places the phenomenon again presented itself, sometimes to myself, sometimes to the lady, and sometimes to both of us simultaneously. The sun was near the horizon on our left hand, and the white surf of the sea was on our right, strongly reflecting the solar rays. It is very probable that the illusion arose from our considering the light as coming from the white surf, in which case the shadows in the hollow foot-prints were such as could only be produced by foot-prints raised from the sand, as if they were in relief. It is possible that, when the phenomenon was observed by Lady Georgiana Wolff, there may have been some source of direct or reflected light opposite to the sun, or some unusual brightness of the clouds, if there were any in that quarter, which gave rise to the illusion.
When these illusions, whether monocular or binocular, are produced by an inversion of the shadow, either real or supposed, they are instantly dissipated by holding a pin in the field of view, so as to indicate by its shadow the real place of the illuminating body. The figure will appear raised or depressed, according to the knowledge which we obtain of the source of light, by introducing or withdrawing the pin. When the inversion is produced by the eyepiece of a telescope, or a compound microscope, in which the field of view is necessarily small, we cannot see the illuminating body and the convex or concave object (the cameo or intaglio) at the same time; but if we use a small inverting telescope, 1½ or 2 inches long, such as that shewn at , Fig. 36, we obtain a large field of view, and may see at the same time the object and a candle placed beside it. In this case the illusion will take place according as the candle is seen beside the object or withdrawn.
If the object is a white tea-cup, or bowl, however large, and if it is illuminated from behind the observer, the reflected image of the window will be in the concave bottom of the tea-cup, and it will not
rise into a convexity if the illumination from surrounding objects is uniform; but if the observer moves a little to one side, so that the reflected image of the window passes from the centre of the cup, then the cup will rise into a convexity, when seen through the inverting telescope, in consequence of the position of the luminous image, which could occupy its place only upon a convex surface. If the concave body were cut out of a piece of chalk, or pure unpolished marble, it would appear neither convex nor concave, but flat.
Very singular illusions take place, both with one and two eyes, when the object, whether concave or convex, is a hollow or an elevation in or upon a limited or extended surface—that is, whether the surface occupies the whole visible field, or only a part of it. If we view, through the inverting telescope or eye-piece, a dimple or a hemispherical cavity in a broad piece of wood laid horizontally on the table, and illuminated by quaquaversus light, like that of the sky, it will instantly rise into an elevation, the end of the telescope or eyepiece resting on the surface of the wood. The change of form is, therefore, not produced by the inversion of the shadow, but by another cause. The surface in which the cavity is made is obviously inverted as well as the cavity, that is, it now looks downward in place of upward; but it does not appear so to the observer leaning upon the table, and resting the end of his eye-piece upon the wooden surface in which the cavity is made. The surface seems to him to remain where it was, and still to look upwards, in place of looking downwards. If the observer strikes the wooden surface with the end of the eye-piece, this conviction is strengthened, and he believes that it is the lower edge of the field of view, or object-glass, that strikes the apparent wooden surface or rests upon it, whereas the wooden surface has been inverted, and optically separated from the lower edge of the object-glass.
In order to make this plainer, place a pen upon a sheet of paper with the quill end nearest you, and view it through the inverting telescope: The quill end will appear farthest from you, and the paper will not appear inverted. In like manner, the letters on a printed page are inverted, the top of each letter being nearest the observer, while
the paper seems to retain its usual place. Now in both these cases the paper is inverted as well as the quill and the letters, and in reality the image of the quill and of the pen, and of the lower end of the letters, is nearest the observer. Let us next place a tea-cup on its side upon the table, with its concavity towards the observer, and view it through the inverting telescope. It will rise into a convexity, the nearer margin of the cup appearing farther off than the bottom. If we place a short pen within the cup, measuring as it were its depth, and having its quill end nearest the observer, the pen will be inverted, in correspondence with the conversion of the cup into a convexity, the quill end appearing more remote, like the margin of the cup which it touches, and the feather end next the eye like the summit of the convex cup on which it rests.
In these experiments, the conversion of the concavity into a convexity depends on two separate illusions, one of which springs from the other. The first illusion is the erroneous conviction that the surface of the table is looking upwards as usual, whereas it is really inverted; and the second illusion, which arises from the first, is, that the nearest point of the object appears farthest from the eye, whereas it is nearest to it. All these observations are equally applicable to the vision of convexities, and hence it follows, that the conversion of relief, caused by the use of an inverting eye-piece, is not produced directly by the inversion, but by an illusion arising from the inversion, in virtue of which we believe that the remotest side of the convexity is nearer our eye than the side next us.
In order to demonstrate the correctness of this explanation, let the hemispherical cavity be made in a stripe of wood, narrower than the field of the inverting telescope with which it is viewed. It will then appear really inverted, and free from both the illusions which formerly took place. The thickness of the stripe of wood is now distinctly seen, and the inversion of the surface, which now looks downward, immediately recognised. The edge of the cavity now appears nearest the eye, as it really is, and the concavity, though inverted, still appears a concavity. The same effect is produced when a convexity is placed on a narrow stripe of wood.
Some curious phenomena take place when we view, at different degrees of obliquity, a hemispherical cavity raised into a convexity. At every degree of obliquity from 0° to 90°, that is, from a vertical to a horizontal view of it, the elliptical margin of the convexity will always be visible, which is impossible in a real convexity, and the elevated apex will gradually sink till the elliptical margin becomes a straight line, and the imaginary convexity completely levelled. The struggle between truth and error is here so singular, that while one part of the object has become concave, the other part retains its convexity!
In like manner, when a convexity is seen as a concavity, the concavity loses its true shape as it is viewed more and more obliquely, till its remote elliptical margin is encroached upon, or eclipsed, by the apex of the convexity; and towards an inclination of 90° the concavity disappears altogether, under circumstances analogous to those already described.
If in place of using an inverting telescope we invert the concavity, by looking at its inverted image in the focus of a convex lens, it will sometimes appear a convexity and sometimes not. In this form of the experiment the image of the concavity, and consequently its apparent depth, is greatly diminished, and therefore any trivial cause, such as a preconception of the mind, or an approximation to a shadow, or a touch of the concavity by the point of the finger, will either produce a conversion of form or dissipate the illusion when it is produced.
In the preceding Chapter we have supposed the convexity to be high and the concavity deep and circular, and we have supposed them also to be shadowless, or illuminated by a quaquaversus light, such as that of the sky in the open fields. This was done in order to get rid of all secondary causes which might interfere with and modify the normal cause, when the concavities are shallow, and the convexities low and have distinct shadows, or when the concavity, as in seals, has the shape of an animal or any body which we are accustomed to see in relief.
Let us now suppose that a strong shadow is thrown upon the concavity. In this case the normal experiment is much more perfect and satisfactory. The illusion is complete and invariable when the concavity is in or upon an extended surface, and it as invariably disappears, or rather is not produced, when it is in a narrow stripe.
In the secondary forms of the experiment, the inversion of the shadow becomes the principal cause of the illusion; but in order that the result may be invariable, or nearly so, the concavities must be shallow and the convexities but slightly raised. At great obliquities, however, this cause of the conversion of form ceases to produce the illusion, and in varying the inclination from 0° to 90° the cessation takes place sooner with deep than with shallow cavities. The reason of this is that the shadow of a concavity is very different at great obliquities from the shadow of a convexity. The shadow never can emerge out of a cavity so as to darken the surface in which the cavity is made, whereas the shadow of a convexity soon extends beyond the outline of its base, and finally throws a long stripe of darkness over the surface on which it rests. Hence it is impossible to mistake a convexity for a concavity when its shadow extends beyond its base.
When the concavity upon a seal is a horse, or any other animal, it will often rise into a convexity when seen through a single lens, which does not invert it; but the illusion disappears at great obliquities. In this case, the illusion is favoured or produced by two causes; the first is, that the form of the horse or other animal in relief is the one which the mind is most disposed to seize, and the second is, that we use only one eye, with which we cannot measure depths as well as with two. The illusion, however, still takes place when we employ a lens three or more inches wide, so as to permit the use of both eyes, but it is less certain, as the binocular vision enables us in some degree to keep in check the other causes of illusion.
The influence of these secondary causes is strikingly displayed in the following experiment. In the armorial bearings upon a seal, the shield is often more deeply cut than the surrounding parts. With binocular vision, the shallow parts rise into relief sooner than the shield, and continue so while the shield remains depressed; but if we
shut one eye the shield then rises into relief like the rest. In these experiments with a single lens a slight variation in the position of the seal, or a slight change in the intensity or direction of the illumination, or particular reflexions from the interior of the stone, if it is transparent, will favour or oppose the illusion. In viewing the shield at the deepest portion with a single lens, a slight rotation of the seal round the wrist, backwards and forwards, will remove the illusion, in consequence of the eye perceiving that the change in the perspective is different from what it ought to be.
In my Letters on Natural Magic, I have described several cases of the conversion of form in which inverted vision is not employed. Hollows in mother-of-pearl and other semi-transparent bodies often rise into relief, in consequence of a quantity of light, occasioned by refraction, appearing on the side next the light, where there should have been a shadow in the case of a depression. Similar illusions take place in certain pieces of polished wood, calcedony, mother-ofpearl, and other shells, where the surface is perfectly plane. This arises from there being at that place a knot, or growth, or nodule, differing in transparency from the surrounding mass. The thin edge of the knot, &c., opposite the candle, is illuminated by refracted light, so that it takes the appearance of a concavity. From the same cause arises the appearance of dimples in certain plates of calcedony, which have received the name of hammered calcedony, or agate, from their having the look of being dimpled with a hammer. The surface on which these cavities are seen contains sections of small spherical formations of siliceous matter, which exhibit the same illusion as the cavities in wood. Mother-of-pearl presents similar phenomena, and so common are they in this substance that it is difficult to find a mother-of-pearl button or counter which seems to have its surface flat, although it is perfectly so when examined by the touch. Owing to the different refractions of the incident light by the different growths of the shell, cut in different directions by the artificial surface, like the annual growth of wood in a dressed plank, the surface of the mineral has necessarily an inequal and undulating appearance.
In viewing good photographic or well-painted miniature portraits in an erect and inverted position, and with or without a lens, considerable changes take place in the apparent relief. Under ordinary vision there is a certain amount of relief depending upon the excellence of the picture. If we invert the picture, by turning it upside down, the relief is perceptibly increased. If we view it when erect, with a lens of about an inch in focal length, the relief is still greater; but if we view it when inverted with the same lens the relief is very considerably diminished.
F . 51.
A very remarkable illusion, affecting the apparent position of the drawings of geometrical solids, was first observed by the late Professor Neckar, of Geneva, who communicated it to me personally in 1832.[73] “The rhomboid ,” (Fig. 51,) he says, “is drawn so that the solid angle should be seen nearest to the spectator, and the solid angle the farthest from him, and that the face should be the foremost, while the face is behind. But in looking repeatedly at the same figure, you will perceive that at times the apparent position of the rhomboid is so changed that the solid angle will appear the nearest, and the solid angle the farthest, and that the face will recede behind the face , which will come forward,
—which effect gives to the whole solid a quite contrary apparent inclination.” Professor Neckar observed this change “as well with one as with both eyes,” and he considered it as owing “to an involuntary change in the adjustment of the eye for obtaining distinct vision. And that whenever the point of distinct vision on the retina was directed to the angle for instance, this angle, seen more distinctly than the other, was naturally supposed to be nearer and foremost, while the other angles, seen indistinctly, were supposed to be farther away and behind. The reverse took place when the point of distinct vision was brought to bear upon the angle What I have said of the solid angles ( and ) is equally true of the edges, those edges upon which the axis of the eye, or the central hole of the retina, are directed, will always appear forward; so that now it seems to me certain that this little, at first so puzzling, phenomenon depends upon the law of distinct vision.”
In consequence of completely misunderstanding Mr. Neckar’s explanation of this illusion, Mr. Wheatstone has pronounced it to be erroneous, but there can be no doubt of its correctness; and there are various experiments by which the principle may be illustrated. By hiding with the finger one of the solid angles, or making it indistinct, by a piece of dimmed glass, or throwing a slight shadow over it, the other will appear foremost till the obscuring cause is removed. The experiment may be still more satisfactorily made by holding above the rhomboid a piece of finely ground-glass, the ground side being farthest from the eye, and bringing one edge of it gradually down till it touches the point , the other edge being kept at a distance from the paper. In this way all the lines diverging from will become dimmer as they recede from , and consequently will appear the most forward point. A similar result will be obtained by putting a black spot upon , which will have the effect of drawing our attention to rather than to .
From these experiments and observations, it will be seen that the conversion of form, excepting in the normal case, depends upon various causes, which are influential only under particular conditions, such as the depth of the hollow or the height of the relief, the distance of the object, the sharpness of vision, the use of one or both
eyes, the inversion of the shadow, the nature of the object, and the means used by the mind itself to produce the illusion. In the normal case, where the cavity or convexity is shadowless, and upon an extended surface, and where inverted vision is used, the conversion depends solely on the illusion, which it is impossible to resist, that the side of the cavity or elevation next the eye is actually farthest from it, an illusion not produced by inversion, but by a false judgment respecting the position of the surface in which the cavity is made, or upon which it rests.
CHAPTER XVII.
ON CERTAIN DIFFICULTIES EXPERIENCED IN THE USE OF THE STEREOSCOPE.
There are many persons who experience great difficulty in uniting the two pictures in the stereoscope, and consequently in seeing the relief produced by their union. If the eyes are not equal in focal length, that is, in the distance at which they see objects most distinctly; or if, from some defect in structure, they are not equally good, they will still see the stereoscopic relief, though the picture will be less vivid and distinct than if the eyes were in every respect equal and good. There are many persons, however, whose eyes are equal and perfect, but who are not able to unite the pictures in the stereoscope. This is the more remarkable, as children of four or five years of age see the stereoscopic effect when the eye-tubes are accommodated to the distance between their eyes. The difficulty experienced in uniting the binocular pictures is sometimes only temporary. On first looking into the instrument, two pictures are seen in place of one; but by a little perseverance, and by drawing the eyes away from the eye-tubes, and still looking through them, the object is seen single and in perfect relief. After having ceased to use the instrument for some time, the difficulty of uniting the pictures recurs, but, generally speaking, it will gradually disappear
F . 52.
In those cases where it cannot be overcome by repeated trials, it must arise either from the distance between the lenses being greater or less than the distance between the eyes, or from some peculiarity in the power of converging the optical axes, which it is not easy to explain.
If the distance between the pupils of the two eyes, , ′, Fig. 52, which has been already explained on Fig. 18, is less than the distance between the semi-lenses , ′, then, instead of looking through the middle portions no, n′o′, of the lenses, the observer will look through portions between o and , and o′ and ′, which have a greater power of refracting or displacing the pictures than the portions no, n′o′, and therefore the pictures will be too much
displaced, and will have so far overpassed one another that the observer is not able to bring them back to their place of union, halfway between the two pictures in the slide.
If, on the other hand, the distance between the pupils of the observer’s eyes is greater than the distance between the semilenses , ′, then, instead of looking through the portions no, n′o′ of the lenses, the observer will look through portions between n and , and n′ and ′, which have a less power of refracting or displacing the pictures than the portions no, n′o′, and therefore the pictures will be so little displaced as not to reach their place of union, and will stand at such a distance that the observer is not able to bring them up to their proper place, half-way between the two pictures in the slide.
Now, in both these cases of over and under displacement, many persons have such a power over their optical axes, that by converging them to a point nearer than the picture, they would, in the first case, bring them back to their place of union, and by converging them to a point more remote than the picture, would, in the second case, bring them up to their place of union; but others are very defective in this power of convergence, some having a facility of converging them beyond the pictures, and others between the pictures and the eye. This last, however, namely, that of near convergence, is by far the most common, especially among men; but it is of no avail, and the exercise of it is injurious when the under refracted pictures have not come up to their place of union. The power of remote convergence, which is very rare, and which would assist in bringing back the over refracted pictures to their place of union, is of no avail, and the exercise of it is injurious when the pictures have been too much displaced, and made to pass beyond their place of union.
When the stereoscope is perfectly adapted to the eyes of the observer, and the general union of the pictures effected, the remote parts of the picture, that is, the objects seen in the distance, may be under refracted, while those in the foreground are over refracted, so that while eyes which have the power of convergence beyond the picture, unite the more distant objects which are under refracted, they experience much difficulty in uniting those in the foreground
which are over refracted. In like manner, eyes which have the power of near convergence will readily unite objects in the foreground which are over refracted, while they experience much difficulty in uniting objects in the distance which are under refracted. If the requisite power over the optical axes is not acquired by experience and perseverance, when the stereoscope is suited to the eyes of the observer, the only suggestion which we can make is to open the eyes wide, and expand the eyebrows, which we do in staring at an object, or in looking at a distant one, when we wish to converge the axes, as in Fig. 22, to a point beyond the pictures, and to contract the eyes and the eyebrows, which we do in too much light, in looking at a near object, when we wish to converge the optic axes, as in Fig. 21, to a point between the pictures and the eye.
When the binocular pictures are taken at too great an angle, so as to produce a startling amount of relief, the distance between similar points in each picture, both in the distance and in the foreground, is much greater than it ought to be, and hence the difficulty of uniting the pictures is greatly increased, so that persons who would have experienced no difficulty in uniting them, had they been taken at the proper angle, will fail altogether in bringing them into stereoscopic relief.
In these observations, it is understood that the observer obtains distinct vision of the pictures in the stereoscope, either by the adjustment of the moveable eye-tubes, if they are moveable, as they ought to be, or by the aid of convex or concave glasses for both eyes, either in the form of spectacles, or separate lenses placed immediately above, or immediately below the semi-lenses in the eyetubes. If the eyes have different focal lengths, which is not unfrequently the case, lenses differing in convexity or concavity should be employed to equalize them.
EDINBURGH: T. CONSTABLE, PRINTER TO HER MAJESTY.
Footnotes:
[1] Edit. of Pena, pp. 17, 18, Paris, 1577; or Opera, by Gregory, pp. 619, 620. Oxon. 1703.
[2] De Usu Partium Corporis Humani, edit. Lugduni, 1550, p. 593.
[3] Joan. Baptistæ Portæ Neap., De Refractione Optices parte, lib v p 132, and lib vi pp 143-5 Neap 1593
[4] Trattata della Pictura, Scultura, ed Architettura. Milan, 1584.
[5] Dr Smith’s Compleat System of Opticks, vol ii , Remarks, pp 41 and 244
[6] Opticorum Libri Sex Philosophis juxta ac Mathematicis utiles. Folio. Antverpiæ, 1613.
[7] In F 1, is the optical pyramid seen by the eye , and the optical pyramid seen by the eye
[8] These angles are equal in this diagram and in the vision of a sphere, but they are inequal in other bodies.
[9] Aguilonius, Opticorum, lib ii book xxxviii pp 140, 141
[10] It is obvious that a complete hemisphere is not seen with both eyes.
[11] Aguilonius, Opticorum, lib. iv. pp. 306, 307.
[12] In the last of these theorems Aguilonius describes and explains, we believe for the first time, the conversion of relief in the vision of convex and concave surfaces See Prop xciv p 312
[13] Id., p. 313.
[14] Opera, tom ii p 394 Lugduni, 1658
[15] Opera Mathematica Optica, tribus libris exposita, p. 136.
[16] Opticks, vol ii , Remarks, pp 41 and 245
[17] Id., vol. i. p. 48, Fig. 196.
[18] Treatise on Optics, p 171; see also sect 64, p 113
[19] Treatise on the Eye, vol i. p. 412, Plate 5, Fig. 37.
[20] As Mr Wheatstone himself describes the dissimilar pictures or drawings as “two different projections of the same object seen from two points of sight, the distance between which is equal to the interval between the eyes of the observer,” it is inconceivable on what ground he could imagine himself to be the discoverer of
so palpable and notorious a fact as that the pictures of a body seen by two eyes two points of sight, must be dissimilar.
[21] Phil. Trans., 1838, pp. 371-394.
[22] Phil. Trans., 1838, pp. 391, 392.
[23] December 28, 1550.
[24] “Le fait est,” says the Abbé Moigno, “que le stéréoscope par réflexion était presque complètement oublié, lorsque Sir David Brewster construisit son stéréoscope par refraction que nous allons décrire ” Cosmos, vol i p 4, 1852
[25] Phil. Trans., 1852, p. 6.
[26] Ibid , pp 9, 10
[27] Vol. v. livre viii. p. 241.
[28] Mr Andrew Ross, the celebrated optician!
[29] The Abbé gave an abstract of this paper in the French journal La Presse, December 28, 1850.
[30] No 54, Cheapside, and 313, Oxford Street The prize of twenty guineas which they offered for the best short popular treatise on the Stereoscope, has been adjudged to Mr. Lonie, Teacher of Mathematics in the Madras Institution, St. Andrews. The second prize was given to the Rev. R. Graham, Abernyte, Perthshire.
[31] Edinburgh Transactions, vol xv p 349, 1843; or Philosophical Magazine, vol xxv pp 356, 439, May and June 1844
[32] Smith’s Opticks, vol. ii., Remarks, p. 107. Harris makes the difference ¹/₁₀th or ¹/₁₁th; Optics, p. 117.
[33] This variation of the pupil is mentioned by Bacon.
[34] Mr Wheatstone himself says, “that it is somewhat difficult to render the two Daguerreotypes equally visible ” Phil Trans , 1852, p 6
[35] A sheet of Queen’s heads may be advantageously used to accustom the eyes to the union of similar figures.
[36] See Edin Transactions, 1846, vol xv p 663, and Phil Mag , May 1847, vol xxx p 305
[37] Bibl. Universelle, October 1855, p. 136.
[38] Smith’s Opticks, vol. ii. p. 388, § 977.
[39] Essay on Single Vision, &c , p 44
[40] We may use also the lens prism, which I proposed many years ago in the Edinburgh Philosophical Journal.
[41] See Chap. i. pp. 33-36.
[42] For 1852, vol. xvii. p. 200.
[43] These solid telescopes may be made achromatic by cementing concave lenses of flint glass upon each end, or of crown glass if they are made of flint glass.
[44] Phil Mag , Jan 1852, vol iii p 19
[45] American Journal of Science, 1852, vol. xv. p. 68.
[46] See my Treatise on Optics, 2d edit , chap vii p 65
[47] See Cosmos, vol. ii. pp. 622, 624.
[48] Id vol vii p 494
[49] Id. vol. iii. p. 658.
[50] Phil Trans , 1852, p 7
[51] Mr. Wheatstone’s paper was published before I had pointed out the deformities produced by large lenses. See p. 130.
[52] The Eye in Health and Disease, by Alfred Smee, 2d edit 1854, pp 85-95
[53] This expression has a different meaning in perspective. We understand it to mean here the point of the sitter or object, which is to be the centre of the picture.
[54] Cosmos, Feb. 29, 1856, vol. viii. p. 202.
[55] It is only in a horizontal direction that we can see 180° of the hemisphere We would require a circle of eyes 2½ inches distant to see a complete hemisphere
[56] See Chapters X. and XI.
[57] When any external light falls upon the eye, its picture is reflected back from the metallic surface of the Daguerreotype, and a negative picture of the part of the Daguerreotype opposite each eye is mixed with the positive picture of the same part
[58] Modern Painters, vol. iii., Preface, pp. 11, 12.
[59] Sir Francis Chantrey, the celebrated sculptor, shewed me, many years ago, a Sketch-Book, containing numerous drawings which he had made with the Camera Lucida, while travelling from London to Edinburgh by the Lakes He pointed out to me the flatness, or rather lowness, of hills, which to his own eye appeared much higher, but which, notwithstanding, gave to him the idea of a greater elevation In order to put this opinion to the test of experiment, I had drawings made by a skilful artist of the three Eildon hills opposite my residence on the Tweed, and was surprised to obtain, by comparing them with their true perspective outlines, a striking confirmation of the observation made by Sir Francis Chantrey.
[60] By using large lenses, we may obtain the picture of an object within the picture of an opaque one in front of it; and with a telescope, we may see through opaque objects of a certain size Many singular experiments may be made by taking photographs of solid objects, simple or compound, with lenses larger than the objects themselves
[61] In a landscape by Mr. Waller Paton, called the “Highland Stream,” now in the Edinburgh Exhibition, the foreground consists principally of a bed of water-worn stones, on the margin of a pool at the bottom of a waterfall The stones are so exquisitely painted, that nature only could have furnished the originals We may examine them at a few inches’ distance, and recognise forms and structures with which we have been long familiar A water-ousel, peculiar to Scottish brooks and rivers, perched upon one of them, looks as anxiously around as if a schoolboy were about to avail himself of the missiles at his feet.
[62] These views are well illustrated by the remarkable photographs of the Crimean war.
[63] A French sculptor has actually modelled a statue from the stereoscopic relief of binocular pictures.
[64] See my Treatise on the Kaleidoscope, second edition, just published
[65] “The importance of establishing a permanent Museum of Education in this country, with the view of introducing improvements in the existing methods of instruction, and specially directing public attention in a practical manner to the question of National Education, has been of late generally recognised.”
Third Report of the Commissioners for the Exhibition of 1851, presented to both Houses of Parliament, p. 37. Lond., 1856.
[66] This fine invention we owe to Mr. Paul Pretsch, late director of the Imperial Printing Office at Vienna. It is secured by patent, and is now in practical operation in Holloway Place, Islington.
[67] An accomplished traveller, the Rev Mr Bridges, who ascended Mount Etna for the purpose of taking Talbotype drawings of its scenery, placed his camera on the edge of the crater to obtain a representation of it No sooner was the camera fixed and the sensitive paper introduced, than an eruption took place, which forced Mr Bridges to quit his camera in order to save his life. When the eruption closed, he returned to collect the fragments of his instrument, when, to his great surprise and delight, he found that his camera was not only uninjured, but contained a picture of the crater and its eruption.
[68] A binocular slide, copied from the one originally designed by myself, forms No 27 of the Series of white-lined diagrams upon a black ground executed in Paris The drawings, however, are too large for the common stereoscope
[69] See Chap. i. p. 15.
[70] Phil Trans 1744
[71] Letter v. pp. 98-107. See also the Edinburgh Journal of Science, Jan. 1826, vol. iv. p. 99.
[72] Journal, 1839, p, 189.
[73] See Edinburgh Philosophical Journal, November 1832, vol. i. p 334
Transcriber’s Notes:
Antiquated spellings were not corrected.
The illustrations have been moved so that they do not break up paragraphs and so that they are next to the text they illustrate.
Typographical and punctuation errors have been silently corrected.
In the Table of Contents, Chapters XV and XVI were corrected from page 200 to 211 and 216 respectively.
Figure 46 was incorrectly labelled Figure 45, this has been corrected.
