XXll PREFACE. 



scientific pursuits, they wish that, whether blame 

 or praise is the fate of their labours, it may be 

 jointly awarded. All that they think necessary to 

 state is, that the composition of each of the dif- 

 ferent departments of the work has been, as 

 nearly as possible, divided between them ; — that 

 though the letter, or series of letters, on any par- 

 ticular subject, has been usually undertaken by 

 one, some of the facts and illustrations have ge- 

 nerally been supplied by the other, and there are 

 a few to which they have jointly contributed ; — 

 and that, throughout, the facts for which no other 

 authority is quoted, are to be considered as rest- 

 ing* upon that of one or other of the authors, but 

 not always of him, who, from local allusions, may 

 be conceived the writer of the letter in which they 

 are introduced, as the matter furnished by each 

 to the letters of the other must necessarily be 

 given in the person of the; supposed writer. 



In acknowledging their obligations to their 

 friends, the first place is due to Simon Wilkin, 

 Esq. of Costessey near Norwich, to whose libe- 

 rality they are indebted for almost all the plates 

 which illustrate and adorn the work; most of 

 which have been drawn and engraved by his 

 artist Mr. John Curtis, whose intimate ac- 

 quaintance with the subject has enabled him to 



