112 HYDROSTATICS, 



sidering what has been already said of the result of 

 the pressure of fluids of equal heights, without any 

 regard to the quantities. For; if a hole be made in 

 the upper board, and a tube be put into it, the 

 water will rise in the tube to the same height that 

 it does in the pipe ; and would rise as high (by 

 supplying the pipe) in as many tubes as the board 

 could contain holes. Now, suppose only one hole 

 to be made in any part of the board, of an equal 

 diameter with the bore of the pipe, and that the 

 pipe holds just one quarter of a pound of water ; 

 if a person put his finger upon the hole, and the 

 pipe be filled with water, he will find his finger 

 pressed upward with a force equal to a quarter of a 

 pound ; and as the same pressure is equal upon all 

 equal parts of the board, each part whose area is 

 equal to the area of the hole, will be pressed up- 

 ward with a force equal to that of a quarter of a 

 pound ; the sum of all which pressures against the 

 under side of an oval board 16 inches broad and 

 18 inches long, will amount to 300 pounds ; and, 

 therefore, so much weight will be raised up and 

 supported by a quarter of a pound of water in the 

 pipe. 



Hence, if a man stand upon the upper board, 

 and blow into the bellows through the pipe, he will 

 raise himself upward upon the board : and the 

 smaller the bore of the pipe is, the easier he 

 will be able to raise himself. Then, by clapping 

 his finger on the top of the pipe, he can sup- 

 port himself as long as he pleases, provided the 

 bellows be air-tight, so as not to lose what is blown 

 into it. 



It is from the pressure of fluids in all directions, 

 that a solid body specifically lighter than a fluid, 



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