502 THE CHEMISTKY OF CEEATION. 



breathe, and oxygen is as necessary to them as 

 it is to ourselves. A simple experiment will 

 illustrate this fact. If one or two gold-fish, in 

 a vessel of water, are placed under the receiver 

 of an air-pump, and the air is gradually ex- 

 hausted therefrom by working the pump, bub- 

 bles of gas will be seen arising from the water, 

 and in a short time the fish will be quite 

 dead after several violent struggles. If, again, 

 fish are placed into a basin of water, which 

 has had all the air expelled by boiling, they 

 will then likewise soon perish : this arises 

 from the want of oxygen, which was contained 

 in a dissolved state in the water. Chemistry 

 informs us, that the proportion of oxygen dis- 

 solved in 100 parts of water is very small 

 (100 cubic inches of water will dissolve about 

 three and a half oxygen); and it is certain, 

 that many other gases, carbonic acid for 

 example, are much more soluble than oxygen. 

 This small proportion is, however, sufficient 

 for the well-being of marine creatures. Had 

 oxygen been very soluble in water, there would 

 have arisen many bad results to the animal 

 world on land, and not less to those of the 

 waters themselves. The effect upon the in- 

 habitants of the deep of a higher charge of 

 oxygen in their respirable medium, would be 

 precisely analogous to its effects upon air- 



