174 OF THE PRESSURE OF UNMIXABLE FLUIDS OF DIFFERENT DENSITIES, 



**=- + *. 



and finally, by transposition, we have 



r 3 (135). 



177. The practical rule for reducing the above equation, may be 

 expressed in words at length in the following manner. 



RULE. Multiply the difference of the cubes of the radii) 

 by the height of the atmospheric column, and divide the 

 product by the cube of the lesser radius for the depth 

 required. 



EXAMPLE. The radius of a globe of condensible matter is 10 inches 

 before immersion, and it is suffered to descend so far as to have its 

 radius diminished to 3 inches ; required the depth of descent, the 

 atmospheric column at the time of the experiment being equivalent 

 to 33 feet. 



Here we have given R 10 inches, r 3 inches, and h 33 feet ; 

 therefore, by proceeding according to the rule, we have 

 R s_ r8 __ 10QO _27 973 ; 



consequently, multiplying by 33 feet, we obtain 



973x33 32109, 

 therefore, by division, it is 



PROBLEM XXIX. 



178. Let a vessel of any form whatever, whose base is hori- 

 zontal, be filled with fluids of different densities which do not 



mix : 



It is required to determine the pressure on the bottom of the 

 vessel, supposing the fluids to succeed each other in the order 

 of their densities. 



Let ABGH represent a vertical section of the 

 vessel, containing fluids of different densities or 

 specific gravities, as indicated by the shading of 

 the several strata AC, DF and EG; and for the 

 sake of simplicity of investigation, let the bottom 

 HG be parallel, and the sides AH, BG perpendicular 



