294 Hydrostatics. 



motion like that in common bellows. Instead of a valve, a 

 pipe AB, about three feet in length, is inserted at B, either 

 in the upper or lower part of the bellows. Now if water be 

 poured into this pipe at A, it will descend into the bellows and 

 gradually separate the pieces EF, CD, from each other by rais- 

 ing the latter ; and if several weights, 200 pounds, for instance, 

 be placed upon the upper board, the small quantity of water in 

 the pipe AB will balance all this weight. More water being 

 poured in, instead of filling the pipe and running over the top A, 

 it will descend into the bellows, and slowly raise the weights; 

 the distance between the surface of the water in the pipe and 

 that in the bellows remaining the same as before. It is manifest 

 from what has been said, that the upward pressure exerted upon 

 each point of the interior surface of CD is sufficient to support a 

 column of fluid of the same height with that contained in the tube 

 AB, and consequently that the whole upward pressure, or weight 

 sustained, is equal to the weight of a cylinder of water, whose 

 base is the area of CD, and whose altitude is that of the column 

 of water in AB above the surface of the water in the bellows or 

 lower surface of CD. The area of the base, for instance, being 

 a foot and a half, and the altitude three feet, the whole mass 

 would be 4 cubic feet, and the weight sustained would be 

 4| X 62t or 281 \ pounds, while the quantity contained in AB, 

 depending on the size of the tube might weigh only one fourth of 

 a pound or any less quantity. 



It is obvious that instead of the gravity of the fluid in the 

 tube AB, any other force might be employed, as the impulse of 

 the breath, or that exerted by a stopper or piston moving in the 

 tube AB. Thus, by means of a lever HI, a dense fluid, as water 

 Fig.197. for instance, might be forced through the pipe CO against a 

 large piston supposed to be accurately fitted to the cylinder FD, 

 arid connected with the rod or bar DE. A valvej being provid- 

 ed at F to prevent the return of the fluid, this action might be 

 repeated ; we should thus have an engine of almost unlimited 



T A cubic foot of water at the temperature of 50 weighs 1000 OZ - 

 avoirdupois or 62l lb ' 



t See note on the construction of valves. 



