15 
can be taken up by the roots of plants, unless 
water is present ; and water or its elements exist 
in all the products of vegetation. The germination 
of seeds does not take place without the presence 
of air or oxygene gas : and in the sunshine, vege- 
tables decompose the carbonic acid gas of the at- 
mosphere, the carbon of which is absorbed, and 
becomes a part of their organized matter, and the 
oxygene gas, the other constituent, is given off; 
and in consequence of a variety of agencies, the 
ceconomy of vegetation is made subservient to the 
general order of the system of nature. 
It is shown by various researches, that the con- 
stitution of the atmosphere has been always the 
same since the time that it was first accurately 
analysed; and this must, in a great measure, de- 
pend upon the powers of plants to absorb or de- 
compose the putrifying or decaying remains of 
animals and vegetables, and the gaseous effluvia 
which they are constantly emitting. Carbonic 
acid gas is formed in a variety of processes of fer- 
mentation and combustion, and in the respiration 
of animals ; and as yet no other process is known 
in nature by which it can be consumed, except 
vegetation. Animals produce a substance which 
appears to be a necessary food of vegetables; 
vegetables evolve a principle necessary to the ex- 
istence of animals ; and these different classes of 
beings seem to be thus connected together in the 
exercise of their living functions, and to a certain 
extent made to depend upon each other for their 
existence. Water is raised from the ocean, diffused 
through the air, and poured down upon the soil, 
