VI PREFACE. 



To the following gentlemen, the author of this work tenders his 

 acknowledgments; to Prof. Edward Hitchcock and Prof. J. W. 

 Webster, who were consulted in the revisal of the earlier proofs ; 

 but to Professors Griscom, Torrey and Olmsted, and to Mr. C. U. 

 Shepard, assistant in the chemical department of Yale College, a 

 more particular expression of thanks is due, for the trouble which 

 they, by request, have taken, in reading nearly all the proofs. Their 

 individual suggestions are occasionally designated ; and while the 

 work has been much benefitted by their judicious criticisms, they are 

 fully exonerated from any responsibility either for its errors, or its 

 deficiences. The errors that have been detected, and which were 

 of such a character as to affect the sense, have been registered, as 

 usual, in a table of errata, although the corrections for most of 

 them are generally obvious from the context. As other errors will 

 doubtless be observed, the author requests, as a particular favor, 

 that they may be promptly communicated to him. 



If it does not excuse, it may account for, some inadvertencies, 

 when it is known, that an arduous and responsible work was written 

 and printed, under the unremitting pressure of absorbing and often 

 conflicting duties. Life is flying fast away, while, in the hope of 

 discharging more perfectly our obligations to our fellow men, we 

 wait in vain, for continued seasons of leisure and repose, in which 

 we may refresh and brighten our faculties, and perfect our know- 

 ledge. After we are once engaged in the full career of duty, such 

 seasons never come ; our powers and our time are placed in inces- 

 sant requisition ; there is no discharge in our warfare ; and we must 

 fight our battles, not in the circumstances and position which we 

 would have chosen, but in those that are forced upon us, by impe- 

 rious necessity. 

 Yale College, 1830. 



