CHAPTER II. 



/ DISCOVERY OF THE PRINCIPLES OF THE 

 * AQUARIUM, AND THE BEST MODE OF 

 tCSV-^ CONSTRUCTING ONE. 



s I stated in my little essay on the 

 formation of a marine Yivarium (en- 

 titled "Ocean Gardens"), the first 

 clearly defined views upon the subject 

 of the mutual interchanges of gases 

 ^ going on between vegetable and animal 

 life, by means of which the vital prin- 

 ciple in each was sustained, were put forth by 

 Lavoisier, Priestley, and Ingenhauss, towards the 

 close of the last century. The theories of Ingen- 

 hauss, especially those concerning the functions of 

 aquatic plants, were announced in greater detail 

 than those of Lavoisier and Priestley, the following 

 passage being found in his last essay : " Plants 

 immersed in water, when exposed to the action of 

 light, emit an air known as oxygen." The know- 

 ledge of this principle is the keystone in the con- 

 struction of the Aquarium. 



The first successful Aquaria were, nevertheless, 



