64: SCIENCE OF COMMON THINGS. 



How fishes ascend and descend in water. Life boats. Cream on milk. 



2. The position and muscular action of a man (when 

 swimming) differ greatly from his ordinary habits ; but 

 beasts swim in their ordinary position. 



389 Why can fat men swim more easily than spare men? 



Because fat is lighter than water / and the fatter a 

 man is, the more buoyant will he be. 



390 How are fishes able to ascend to the surface of water f 



I Fishes have an air-bladder near the abdomen ; when 

 this air-vessel is distended, the fish increases in size 

 and (being lighter) ascends through the water to its 

 surface. 



391 How are fishes able to dive in a minute to the bottom of a stream f 



They compress the air in their air-bladder ; in conse- 

 quence of which their size is diminished, and they sink 

 instantly. 



393 Why does the body of a drowned person rise and float upon the 

 surface several days after death ? 



Because, from the accumulation of gas within the 

 body (caused by incipient putrefaction), the body be- 

 comes specifically lighter than water, and rises and 

 floats upon the surface. 



393 How are life-boats prevented from sinking ? 



They contain in their sides air-tight cells, or boxes 

 filled with air, w T hich by their buoyancy prevent the 

 boat from sinking even when it is filled with water. 



394 The slaves of the West Indies have a plan of stealing rum from a 

 cask, by inserting the long neck of a bottle, full of water, through the bung. 

 How are they enabled in this manner to obtain the rum ? 



The rum is very much lighter than the water / and 

 as the heavy water falls out of the bottle into the cask, 

 the lighter rum rises to take its place. 



395 Why does cream rise upon milk ? 



Because it is composed of particles of oily or fatty 

 matter, which are lighter than the watery particles of 

 the milk. 



396 Why do stale eggs fioat upon water? 



Because, by keeping, air is substituted for a portion 

 of the water of the egg, which escapes. 



