130 



WELLS'S NATURAL PHILOSOPHY. 



Fig. 111. immense pressure on the body 



exerted by the water. It is prob- 

 able, also, that there is a limit of 

 depth beyond which each spe- 

 cies of fish can not live. The 

 principle of the equal transmis- 

 sion of pressure by liquids, how- 

 ever, enables fishes to sustain a 

 very great pressure of water 

 without being crushed by it; 

 the fluids contained within them 

 pressing outward with as great a 

 force as the liquid which sur- 

 rounds them presses inwards. 

 When a ship founders at sea, the great pressure at the bottom forces the 



water into the pores of the wood, and increases its weight to such an extent 



that no part can ever rise again. 



Upon what does 295. The pressurG upon the bottom of a vessel 

 containing a liquid, is not effected by the shape 

 of the vessel, but depends solely upon the area 

 of the base, and its depth below the surface. 



This arises fi-om the law of equal distribution of pressure in liquids. Fig. 



112 represents two different vessels 

 having equal bases, and the same per- 



tlie pressure 

 upon the bot- 

 tom of a vessel 

 containing; liq- 

 uid depend ? 



Fig. 112. 



\D 



-JP.. 



,.C; pendicular depth of water in them- 

 i Although tlie quantity of water con- 

 J tained in one is much greater than in 

 the other, the pressure sustained by 



B A B these bases will be thesame. 



In a conical vessel. Fig. 113, the 

 base, C D, sustains a pressure measured by the heiglit of the column, ABC 

 D ; for all the rest of the liquid only presses on A B C D laterally, and resting 



Fig. 113. Fig. 114. 



on the aides, E C and F D, can not contribute any thing to the pressure ot 

 the base, C D. But ui a conical vessel, of the shape represented in Fig. 114, 



