viij

PREFACE.

all the perfection that it is possible to achieve. So that one may know to what extent the strength of men and horses can be reduced in the various postures they are obliged to assume to move a machine, rules suitable to this subject have been derived from reasoning and experience.

To perfectly fulfill the objective of this Work, it was believed necessary to teach everything essential that could be said about the movement of Waters; this is also the section that will be found to have been crafted with the most care. It treats the leveling and equilibrium of Liquids original: "Liqueurs"; used here in the general historical sense of any fluid substance, specifically water in this context., and the action of water against the walls of the vessels containing it, in order to derive rules for measuring its thrust and proportioning the resistance that can be opposed to it by cofferdams original: "Bâtardeaux"; temporary watertight enclosures pumped dry to allow construction work below the waterline., dikes, levees, sluices original: "Ecluses"; structures used to control water levels or flow in a canal or river., and so forth. It then shows the manner of measuring the discharge original: "dépense"; the volume or rate of water flow passing through an opening. of water flowing through apertures or sluice-gates original: "Orifices ou Pertuis"; "pertuis" refers specifically to narrow openings or vents in hydraulic structures., in whatever direction they may be, and how one can estimate the loss caused by friction against the edges, as well as how one should calculate the force of the impact of currents against opposing surfaces; and finally, what happens to bodies submerged in water, whether they float or sink to the bottom.

Water being, of all agents, the one from which the greatest advantage is derived for operating machines, the entire Second Book revolves around the application that can be made of it to the wheels of different types of mills, and the speed they must have relative to the current that moves them, so that the machine is capable of the greatest effect. Descriptions of several types of very ingenious grain mills original: "Moulins à bled"; mills used for grinding grain into flour. are given there; the way to discover through calculation the force required to move them, and the output of which they may be capable, relative to the weight and speed of the millstone. Included in these calculations is the resistance caused by friction, and everything that might be