1846.] Theory of Agriculture. 5 



with the variations in the products which may result from an 

 exposure to a variety of causes. 



The rang-e of such a formula does not require that we should 

 know what lite is, in the abstract, nor how living organized 

 matter acts upon the dead, in order to assimilate it ; neither is it 

 required that we should determine aforehand whether life is an 

 independent principle, or whether it is a mere result of chemi- 

 cal and physical action. 



With these preliminary remarks, we proceed more directly to 

 those points which bear upon the subject before us. 



In the first place, it will be necessary to say a few words upon 

 the elements concerned in vegetation, by which we mean the 

 proximate elements, rather than the simple undecompounded 

 ones ; for the former are rarely, if ever, received uncombined 

 into the vegetable tissues. The whole number of elementary 

 bodies now known amounts to 54 or 55 ; but of this number 

 only about fourteen are of importance in vegetation. Even of 

 these, only a few seem to possess such a general range of affin- 

 ity as to be always present in a vegetable tissue. We are in 

 the habit of estimating the importance of a substance by the fre- 

 quency of its presence and the quantity or percentage in which 

 it enters into combination. There is sometimes, however, an 

 importance which is not indicated by this rule ; for instance, 

 oxygen, which constitutes nearly one-half of the solid matter 

 of the globe, has an importance above other elements, which is 

 not measured by quantity or universality ; thus in the execu- 

 tion of a function, it possesses a pre-eminence, and may be 

 termed, with propriety, a controlling element. 



No organized being is destitute of it, neither in the condition 

 in which things are constituted here, can any living thing ex- 

 ist without it. Indeed, they seem to have been created with a 

 direct reference to it, and to be so subordinated to its properties 

 that life is conditioned upon its existence. 



Carbon, too, ranks high as an element in all organized bodies. 

 As a solid material, it is more abundant in the vegetable king- 

 dom than all the rest put together ; though, in some structures 



