PRKFACK. XXm 



give to the figures an accuracy which they could 

 not have received from one less conversant with 

 the science. Nor is the reader less under obliga- 

 tion to Mr. Wilkin's liberality than the authors, 

 who, if the drawings, &c. had been to be paid 

 for, must necessarily have contented themselves 

 with givino' a much smaller number. 



To Alexander MacLeay, Esq. they are 

 under particular obligations, for the warm in- 

 terest he has all along taken in the work, the ju- 

 dicious advice he has on many occasions given, 

 the free access in which he has indulged the 

 authors to his unrivalled cabinet and well-stored 

 library, and the numerous other attentions and 

 accommodations by which he has materially as- 

 sisted them in its progress. 



To the other friends who have kindly aided 

 them in this undertaking in any way, they beg 

 here to offer their best thanks. 



