LIFE ON THE EARTH. 5 



like their Divine Author, independent of time and 

 exempt from change. 



ESSENTIAL CONDITIONS OF LIFE. 



The Forces of Nature are constant ; we do not 

 conceive of them as beginning, or changing, or end- 

 ing ; the Laws of Nature appear to us invariable ; 

 but the forces and the laws are manifested only in 

 relation to particular conditions. Thus in the case 

 of life, regarded as a manifestation of forces accord- 

 ing to laws, we find it to be limited to f organic' 

 structures composed of certain sorts, and certain 

 combinations of matter 1 . Much of the matter which 

 composes living bodies is capable of assuming the 

 gaseous form, as Carbon, Hydrogen, Oxygen, Nitro- 

 gen. Other parts are capable of appearing in 

 solution, as Phosphate of Lime, Carbonate of Lime, 

 &c. All the substances named exist in nearly all 

 plants and animals ; and it appears, though we do 

 not know how, necessary to the exhibition of vital 

 phenomena, that they should be present necessary, 

 I mean, according to this actual plan of creation, 

 the only one we are acquainted with, or can justly 



1 In modern language matter is said to be known to us only 

 by effects cognizable by our senses; these effects are due to 

 forces ; matter is the seat of these forces ; or, if we will, it is a 

 collection of centres of force. 



