204 



MACHINERY IN CONNECTION WITH WATER. 



with a force exactly equal to its own weight ; that is, if 

 there is a pound of water, it will press on the bottom with 

 a force equal to one pound. Now, if the bottom be pushed 

 upward, so as to drive the water into the 

 narrow part of the vessel, the pressure upon 

 the bottom becomes instantly much greater, 

 or equal to many pounds, the water being 

 the same in quantity, but with a much 

 higher head than before. Suppose the nar- 

 row part of the vessel is twenty times 

 smaller than the larger part, then, in pushing 

 ( I the bottom up one inch, the water is driven 



twenty inches upward in the tube. So then, 

 according to the rule of virtual velocities, it will require 

 twenty times the force, because it moves upward twenty 

 times faster.* This, then, is precisely similar to the in- 

 stance where a pound on the longer end of a steelyard 

 balances twenty pounds on the shorter ^ig. 232. 



end. In this instance, the upper parts, 

 T> D, of the vessel operate as the fulcrum 

 of a lever, and offer resistance to the slid- 

 ing part as soon as the water begins to 

 ascend the tube. 



HYDROSTATIC BELLOWS. 



This prhiciple is shown in the J3y- ^^~=^" 

 drcstatic Bellows (fig. 232), which con- 

 sists of two round pieces of board. Hydrostatic Bellows. 



connected by a narrow strip of strong leather; into it is 

 inserted a long, narrow tube, B, with a small funnel, e, at 

 the top. When water is poured into this tube, it will 

 raise a weight as much greater than the weight of the 



* The pressure will be as great upon the bottom us if the vessel con- 

 tinued a uniform size all the way up. 



