PUMPS AS RATCHET-TRAINS.
477
with twice as great a velocity as it is raised by the other. It is not necessary that the pumps should be placed side by side in this arrangement ; in some cases they are arranged with the two barrels one above the other and conaxial, one pump being driven from above and one from below.*
The double-acting ratchet-train of Lagarousse, shown once more in Fig. 354, is represented by a double-acting Vose pump, Fig. 355.
FIG. 350.
FIG. 351.
The analogy can again be followed out through every detail ; here again we find, too, that the velocity of the one piston relatively to the water is always twice as great as its velocity relatively to the frame, just as in the case of the clicks I and \ and the wheel a.
In a similar way we find in pumps of other constructions a com- plete analogy with ratchet-trains. The differences are simply those permitted or rendered necessary by the fluidity of the
- Cf. Konig's Pumpen, p. 52. In Prunier's pumps at the Vienna Exhibition,
the two barrels are conaxial and the rod of the upper plunger is made hollow, that of the lower one passing through it. They are thus both worked from above. See Record of Vienna Univ. Ex. (Maw and Dredge) PI. Ixvii.
