The Book of Mechanics

For let there be two weights AB on a lever, A the greater, B the lesser; of which, when disposed together on the lever in this way, the center of gravity is C. But let the fulcrum be under the lever between C and A at D. And since the weights AB are inclined towards the center of gravity C, then C will naturally be moved downwards; and consequently the weight B will also tend downwards. But if B is moved downwards, A will certainly be raised upwards, seeing that, although as a heavy thing—and released without the connection of weight B—it would tend downwards; yet as it is attached to weight B, by the intervention of the lever AB, it will be moved upwards; and (if I may say so) the weight A would naturally ascend against its own nature. Whence it is clear that these movements are natural effects. What, therefore, does art itself effect? Truly nothing other than that it so disposes and adapts things that similar effects proceed from them as if they were entirely natural; wherefore it will be necessary for Art to imitate nature, since natural effects ought to result. Therefore, it disposes the lever and the fulcrum in the same way, and in place of weight B, it establishes some power which, by pressing, has a force equal to the gravity of B itself; and then the moving power itself, which is less than the gravity of weight A, will nevertheless lift the heavier A: which, although it is repugnant to its own nature, will nevertheless be carried upwards naturally by that power existing in B; for things so disposed have such a nature that A must be moved upwards, but B downwards. Which things, indeed, will be rendered most certain from our book of Mechanics and from those things which are treated therein; and what we have said of the lever is also to be understood of other mechanical instruments. The apparatus of which are works of art, but their effects are almost those of nature; since they follow its moments and inclinations as the chief causes of such works; since they are entirely admirable and most excellent, as can be clear from the contemplation of them; of which matter, let it be enough to have indicated this argument: namely, that they have been treated by the greatest men, Aristotle and Archimedes.