HYDROSTATICS. 115 



oF wood will not rise from the lower one; for as the 

 upper one is pressed down, both by its own weight 

 and the weight of all the water over it, whilst the 

 contrary pressure of the water is kept off by the 

 wood under it, it will lie as still as a stone would 

 do in its place. But if it be raised ever so little at 

 any edge, some water will then get under it, which 

 being acted upon by that above, will immediately 

 press it upward; and as it is lighter than its bulk of 

 water, it will rise and float upon the surface. 



If two fluids of different densities are included 

 in the separate branches of a bent tube, they will 

 balance each other, when the altitudes above their 

 common junction are reciprocally proportional to 

 their specific gravities: thus a column of mercury 

 will balance fourteen its height of water, because 

 mercury is fourteen times as heavy as water. 



The most elegant and useful application of the 

 principle of the hydrostatic paradox is, in Bramah's 

 hydrostatic press, represented Plate 25. fig. 3. : a b 

 is a small forcing pump, the piston of which is 

 worked by the handle or lever, A B. This pump 

 forces the water through the pipe, bed, into the 

 bottom of the thick pipe, E F : also containing a 

 piston that exactly fits the inside ; to this piston is 

 attached a rod, G, working through a collar of 

 leathers in the top of the wide cylinder: the rod, G, 

 performs the work by pressing against whatever is 

 required. The power of this machine will be in 

 proportion to the areas of the surfaces of the two 

 pistons, or as the squares of their diameters. Thus 

 supposing the diameter of the large cylinder to be 

 six inches, andthat of the small cylinder to be £ inch, 

 the diameters will be as 1 to 24, and the areas will be 

 as 1 to 576. Therefore, if the small piston be forced 



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