Miscellaneous. 



425 



to new forms of organic life. Geologists have examined their remains, 

 and endeavoured to form conceptions of the physical characters of 

 the globe during their residence on it. They have drawn legiti- 

 mate conclusions, from the order of their occurrence, regarding several 

 grand eras in the history of the world. These inferences have been 

 deduced from external characters possessed by animals and plants 

 occurring in particular formations ; and, by a happy application of 

 analogical reasoning, they have shewn what must have been the 

 aspect of the face of nature when these plants and animals existed. 

 Why, therefore, should the chemist be afraid to follow in their foot- 

 steps ; and by evidences drawn from the chemical composition of 

 matter, lend his aid in explaining the mighty revolutions which 

 have taken place upon the surface of the earth? True, his science 

 is not speculative, nor does he love to waste his time in the vagaries of 

 theoretical speculation ; but, we believe, that the evidences existing 

 on the earth are sufficient to form a basis for inductive reasoning, 

 without the necessity of substituting ideas for facts. 



I shall, therefore, endeavour to lay before you this evening an 

 account of some of the chemical causes which have led to the de- 

 velopment of the various races of animals and vegetables, which 

 have appeared and disappeared in their course. And be it remarked 

 at the threshold of our enquiry, that by the term chemical causes, 

 we do not at all mean to undervalue the physical causes which have 

 lent their aid or been paramount, in their development or extinc- 

 tion, but merely employ the term to form a boundary in the exa- 

 mination of a boundless subject. 



But, before I can make myself understood, it is absolutely neces- 

 sary that you should be acquainted with the laws which regulate 

 the nutrition of the vegetables now existing on the earth. Mr. 

 Ransome, in a series of lectures, has so ably performed this task, 

 that little remains for me, except to refresh your memory with a 

 few of the grand laws connected with vegetable nutrition. You are 

 all aware that organic matter, in general, is composed of four sub- 

 stances, carbon or charcoal, oxygen, hydrogen, and nitrogen. You 

 know, that when charcoal unites with oxygen, it forms a gas familiar 

 to you as the air which escapes in small bubbles from champagne or 

 beer, and which has received the name of carbonic acid gas. You 

 know also that when oxygen unites with hydrogen, the familiar sub- 

 stance, water, is produced; and that when the latter element 

 (hydrogen) enters into union with nitrogen, ammonia or hartshorn 

 is the product. 



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