66 



ON THE GENERAL DIFFUSION OF KNOWLEDGE. 



Fig. 6. 



W 



c 



Fig. 7. 

 K 



board, and pour more water into the pipe, it 

 will run into the bellows, and raise up the 

 board with all the weights upon it. And though 

 the water in the tube should weigh in all only a 

 quarter of a pound, yet the pressure of this 

 small force upon the water below in the bellows 

 shall support the weights, which are 300 pounds ; 

 nor will they have weight enough to make them 

 descend, and conquer the weight of water, by 

 forcing it out of the mouth of the pipe. The 

 reason of this will appear from what has been 

 already stated respecting 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 it would rise as high (by sup 

 plying the pipe) in as many tubes as the board 

 would contain holes. 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 will he be able to raise him 

 self. And if he put his finger on the top of the 

 pipe he may support himself as long as he 

 pleases. 



The uges to which this power may be applied 

 ttf of great variety and extent ; and the branches 



of art dependent upon it appear to be yet in the K 

 infancy. By the application of this power the 

 late Mr. Bramah formed what is called the Hy 

 drostatic Press, by which a prodigious force is 

 obtained, and by the help of which, hay, straw, 

 wool, and other light substances, may be forced 

 into a very small bulk, so as to be taken in 

 large quantities on board a ship. With a ma 

 chine, on this principle, of the size of a tea-pot, 

 standing before him on a table, a man is enabled 

 to cut through a thick bar of iron as easily as he 

 could clip a piece of pasteboard with a pair of 

 sheers. By this machine a pressure of 500 of 

 600 tons may be brought to bear upon any sub 

 stances which it is wished to press, to tear up, 

 to cut in pieces, or to pull asunder. 



Upon the same principle, the tun or hogshead 

 HI, fig. 7, when filled with water, may be 

 burst, by pressing it with some pounds addi 

 tional weight of the fluid through the small tube 

 KL, which may bfi supposed to be from 25 to 

 30 feet in height. From what has been already 

 stated, it necessarily follows, that the small 

 quantity of water which the tube KL, contains, 

 presses upon the bottom of the tun with as much 

 force as if a column of water had been added as 

 wide as the tun itself, and as long as the tube, 

 which would evidently be an enormous wight, 



