INTRODUCTION. 29 



which a character of greater elevation may be imparted to 

 the study of nature. By the suppression of all unnecessai-y 

 detail, the great masses are better seen, and the reasoning 

 faculty is enabled to grasp all that might otherwise escape the 

 limited range of the senses. 



The exposition of general results has, it must be owned, 

 been singularly facilitated by the happy revolution experienced 

 since the close of the last century, in the condition of all the 

 special sciences, more particularly of geology, chemistry, 

 and descriptive natural history. In proportion as laws admit 

 of more general application, and as sciences mutually enrich 

 each other, and by their extension become connected together 

 in more numerous and more intimate relations, the develop- 

 ment of general truths may be given with conciseness devoid 

 of superficiality. On being first examined, all phenomena 

 appear to be isolated, and it is only by the result of a multi- 

 plicity of observations, combined by reason, that we are able to 

 trace the mutual relations existing between them. If, how- 

 ever, in the present age, which is so strongly characterised by 

 a brilliant course of scientific discoveries, we perceive a want 

 of connection in the phenomena of certain sciences, we may 

 anticipate the revelation of new facts, whose importance will 

 probably be commensurate with the attention directed to these 

 branches of study. Expectations of this nature may be 

 entertained with regard to meteorology, several parts of 

 optics, and to radiating heat, and electro-magnetism, since the 

 admirable discoveries of Melloni and Faraday. A fertile field 

 is here opened to discovery, although the voltaic pile has 

 already taught us the intimate connection existing between 

 electric, magnetic, and chemical phenomena. Who will 

 venture to affirm that we have any precise knowledge, in the 

 present day, of that part of the atmosphere which is not 

 oxygen, or that thousands of gaseous substances affecting our 

 organs may not be mixed with the nitrogen, or finally, that we 

 have even discovered the whole number of the forces which 

 pervade the universe : 



It is not the purpose of this essay on the physical history of 

 the world to reduce all sensible phenomena to a small numbei 

 of abstract principles, based on reason only. The physical 

 aistory of the universe, whose exposition I attempt to deve- 

 iope, does not pretend to rise to the perilous abstractions of a 



