VOLUME
III
on the quantity of water whether a mili grinds a lot or a little. A small quantity may do it, if it goes through an enclosed channel for it then will hold the water much more concentrated than in an open channel, and therefore when enclosed it conveys the water much better to strike the wheel. So then, this kind of flume-mill should have a much more level channel as has been said many times. If it should be mounted quite upright along the diagonal of its square, the wheel would go very heavily because it would be struck from on top downwards. So the water should come to strike the wheel obliquely, as can be understood by rules of geometry and also of philosophy, because in these matters sorne little practica! imagination will make its contribution. Yet it should be known what effect the lines produce when they strike on one part rather than another, and conformably, how the thing is to be fixed or sited, whether it is striking a wheellike a cartwheel or one laid like a millstone. So then, there are various methods, positions or locations for the wheels Ăust as in the location or place where the thing is to be put. Therefore, to fĂx things straight, in this as in anything else, use a little imagination especially for the waterwheel and the shaft. The covered channel which they call flume should be much wider where the water enters than at the other end where it pours out . At the wide end it should be four parts and where it is narrower, it is to be but one of those parts in width; it is to be at least thirty palms long because the longer the channel, the greater the force carried by the water. This flume should be made in proportion and with ingenuity. [!fol. 291v] Consider if there is plenty of water or but little, because the channel must be made large or small according to the quantity of water. so the same rule will hold which has been given in general for channels; they should be thirty-two palms long, and four palms at the mouth and one palm in the base, not wider nor larger because much water may go through one palm; although I would wish that the flume be narrower and deeper in the part where the water is discharged so that it may strike the blades more broadly. Yet the quantity of water should not be too deep, as if we were to say that the water should be not more than one and a half palms in width and half a palm in depth. In this way the water will have much more force than a palm square on all four sides. When these channels have a small quantity of water they should be placed more vertically than when they have a large quantity of water. Here I shall set clown a few types of channels in order that my ideas in this matter of the channels may be better understood; and this is to be understood of oak as of stone and of any other kind of nozzles or of channels, covered or open. These are different; here below are the variations according to the amount of water. allustratt'on 182) Illustration 182
Less Equal More
D
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PUNDACIĂ“N JuANELO TURRIAKO