X rREFACE. 



who have lately done so much for the improvement 

 of this part of science. We expect of any person who 

 should undertake a work of this description, that he 

 should be gifted, in the second place, with that sound 

 judgment in matters of speculation, which may pre- 

 vent him from being led aside, by the very beauty of 

 the facts which he has to disclose, into theories that 

 are rather amusing or adventurous than well found- 

 ed ; that he should cherish, in short, that truly philo- 

 sophical spirit which spurns equally the contracted 

 views of vulgar minds, and the fanciful reveries of 

 men of genius and enthusiasm. We expect of him, 

 in the last place, that he should not only think sound- 

 ly and philosophically, but that he should also have 

 the kindred talent of disposing his reasonings in the 

 most luminous order, and that his work should imi- 

 tate the great system of nature, of which it professes 

 to illustrate a part, by having all things well arranged, 

 and in due proportion. 



The Translator of the work which is now offered 

 to the public, is not expressing his own conviction 

 merely, but that of men much better qualified than 

 himself to form a correct opinion upon this subject, 

 when he ventures to claim for this Treatise all the ex- 

 cellencies which the qualities now enumerated are ne- 

 cessary to secure. The extent of reading which has 

 been gone through for obtaining the materials of tlie 

 work, may be seen from the list of authors prefixed 

 to its more important chapters ; and perhaps there is 



