Volume I
minutes. The board is A, the minute circle C, and an indicator D. Above this indicator is another much smaller circle, also marked all round in equal sections; and upon it another indicator no bigger than this circle. This has hundredths marked between the sixteenths. The small circle is E, its indicator F. They are fixed with an iron peg, G, to hold them firm, so although indicator D goes round, circle D does not move, nor yet does D move when indicator F does. Of these two wheels, one will serve for the gain, the other for the loss: so we can say that one is for ascent, that is, what is lost, and the other for descent, that is the gain made for conveying water. That is the reason we call them by these names; as the ground over which we are levelling rises, the indicators go in opposite directions to one another, both the large ones and the small in each wheel. (Illustration 14) l/fol. 52v] There is another instrument, which Junior Columella in his De Re Rustica calls a ciconia2. It is made in the fashion of a cross or letter X in the alphabet. On this cross is laid another piece, like the Latin letter T, to which a weight is attached, in order to know the rise and fall of what we are levelling. This instrument is marked on the sides of the cross, to show how the T descends in the centre of the cross. It works differendy from the other instruments or levels. The T is A, B; and C is where the cathetus or weight is suspended; D is the centre of the cross, E, F, G, H the cross itself. The ends and weight are I. On the two upper arms, K and L, the minutes are marked by their lines, as is proper to such instruments. All four arms must needs be equal, as if they were to be placed within a perfect square, touching its four angles. Ufol. 53r] There is another instrument called a step level3. It is very different in shape and construction from the rest, even though it serves the same purpose, but in a different way, and to greater effect. With it, the vertical and horizontal dimensions of the route that is being surveyed are precisely measured; also the profundity or depth may be known, which is not done by any of the other levels. The method of construction is like this: a wooden foot is made, like a stand on which candles are placed, and in the centre a rule is mounted. It is to be of a very hard dry wood, without any knots, three fingers square in thickness, at least fifteen palms in height, with straight grain, and perfectly squared off. The most it could have in height would be twenty palms, or less, as each one thinks best. The foot is ' to be made conformable to the height of the rule, and is to be triangular. At the top of the rule a transom is to be fixed, like a square, well fastened to the rule so that it can not make any movement. The transom is to have at both ends pulleys, with free play, over which passes a cord, with a weight at one end, the other being fastened to the foot. [/fol. 53v] This cord is to be long enough to touch the ground, and even further, so that in surveying down hill it will reach the ground. The rule 2 'another instrument which Junior Columella ... calls «ciconia»'. Not illustrated, although a space is provided. Columella's title and the instrument's name are given in Latin; Columella was the guide to high farming Roman-style and remained popular in the sixteenth century. 'De Re Rustica (111.13.11)' describes the «ciconia», but its purpose is to ensure that the trenches in which vines were to be planted should be level, to regulate their size, so that it was not really a level; as proposed here, it becomes an alternative form of A-level. 3 'another instrument called a step-level'. The «nivel de grados», whose shape seems to be modelled on a crane; again, apparently intended to translate an angle into vertical and horizontal lines. But, either it is assumed that the angle of slope will remain constant all the way up a ridge, or it will be necessary to move the level forward many times, placing the stand where the weight last touched, and then repeating the action; a very cumbersome procedure. Here the cord is wound round the axle of the dial, so that it can be read off each time.