31. A Wheel in a Temple, which, on being turned, liberates purifying Water.
In the porticoes of Egyptian temples revolving wheels of bronze are placed for those who enter to turn round, from an opinion that bronze purifies. There are also vessels of lustral water, from which the worshippers may sprinkle themselves. Let it then be required so to construct a wheel that, on turning it round, water shall flow from it to sprinkle the worshippers as we have described. Behind the entrance-pillar let a vessel of water, A B C D (fig. 31), be concealed, having a hole, E, perforated in its base. Underneath the base let a small tube, F G H K, be fastened, having also a hole bored opposite the orifice in the base, and within this place another tube, L M, soldered to the tube F G H K at L, and opposite the orifice having in like manner a hole, S: between these two pipes let another pipe, N X O R, be closely fitted, with a hole at P opposite to E. Now, if the several holes are in one line, when water is poured into the vessel A B C D it will flow out through the pipe L M; but, if the pipe N X O R is made to revolve so as to change the position of the hole P, the discharge will cease. Attach the wheel to the pipe N X O R, and, if it is repeatedly made to revolve, water will flow out.