CHAPTER II. 
I DISCOVERY OP THE PRINCIPLES OP THE 
^ AQUARIUM, AND THE BEST MODE OP 
CONSTRUCTING ONE. 
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s I stated in my little essay on the 
formation of a marine Vivarium (en¬ 
titled “ Ocean Gardens 5 ’), 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, w r ere 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, 
