The fall of water onto mill wheels
Water turns a wheel by the continuous pressure of its weight, not by percussion
Under the heading 'On the fall of water onto mill wheels' (text 1) the page argues that among falls of water at various obliquities little difference is found, working the geometry of a perpendicular fall e f against an oblique fall b o and the half-height X to e (text 3). It then states the principle that water turns a wheel by weight and continuous pushing, not by blow, since percussion acts only in indivisible time at the first instant of contact. A long analysis of the sound of falling water — through a pipe versus surrounded by air — supports the claim. A geometric diagram at the top labels the fall with points b c d e, f, m, n, o, a x r (text 2).
On this page
Little difference among oblique falls of water on mill wheels
For a fall to work at the first degree of its power it must drop along a perpendicular line, as at e f; yet moving from e and striking f it falls only half the height from X to e, so it has little strength. An oblique fall along b o strikes lower at o but loads so heavily on its channel that it does no more work than e did at f.
Water turns the wheel by weight, not by percussion
The waters falling on mill wheels move them with force equal only to the simple weight of the water; it is weight, not the blow, that does the work, since percussion acts only at the first arrival and in indivisible time. The sound of falling water, whether guided through a pipe or twisting in the air, is used to prove that continuous noise does not mean continuous percussion.
Diagram of the water fall onto the wheel
A schematic at the top of the page traces the geometry of the falling water and the wheel it strikes, labelled with the points b c d e, f, m, n, o, a x r. The lettering keys the perpendicular fall e f and the oblique line b o discussed in the text.