[Illustration 182 (Suction Pumps): A--Tappets of piston-rods. B--Cams of the barrel. C--Square upper parts of piston-rods. D--Lower rounded parts of piston-rods. E--Cross-beams. F--Pipes. G--Apertures of pipes. H--Trough. (Fifth kind of pump--see p. 181).]
The fifth kind of pump is still less simple, for it is composed of two or three pumps whose pistons are raised by a machine turned by men, for each piston-rod has a tappet which is raised, each in succession, by two cams on a barrel; two or four strong men turn it. When the pistons descend into the pipes their discs draw the water; when they are raised these force the water out through the pipes. The upper part of each of these piston-rods, which is half a foot square, is held in a slot in a cross-beam; the lower part, which drops down into the pipes, is made of another piece of wood and is round. Each of these three pumps is composed of two lengths of pipe fixed to the shaft timbers. This machine draws the water higher, as much as twenty-four feet. If the diameter of the pipes is large, only two pumps are made; if smaller, three, so that by either method the volume of water is the same. This also must be understood regarding the other machines and their pipes. Since these pumps are composed of two lengths of pipe, the little iron box having the iron valve which I described before, is not enclosed in a trunk, but is in the lower length of pipe, at that point where it joins the upper one; thus the rounded part of the piston-rod is only as long as the upper length of pipe; but I will presently explain this more clearly.
[Illustration 183 (Suction Pumps): A--Water-wheel. B--Axle. C--Trunk on which the lowest pipe stands. D--Basket surrounding trunk. (Sixth kind of pump--see p. 184.)]
The sixth kind of pump would be just the same as the fifth were it not that it has an axle instead of a barrel, turned not by men but by a water-wheel, which is revolved by the force of water striking its buckets. Since water-power far exceeds human strength, this machine draws water through its pipes by discs out of a shaft more than one hundred feet deep. The bottom of the lowest pipe, set in the sump, not only of this pump but also of the others, is generally enclosed in a basket made of wicker-work, to prevent wood shavings and other things being sucked in. (See p. 183.)