xii 



PREFACE. 



Throughout the whole pubHcation, wherever any 

 fact of importance not depending on their own au- 

 thority is mentioned, a reference to the source whence 

 it has been derived is generally given ; so that, if 

 the work should have no other value, it will possess 

 that of saving much trouble to future inquirers, by 

 serving as an index to direct them in their re- 

 searches. 



The Authors are perfectly sensible that, notwith- 

 standing all their care and pains, many imperfections 

 will unavoidably remain in their work. There is no 

 science to which the adage, Dies diem docet, is more 

 strikingly applicable than to Natural History. New 

 discoveries are daily made, and will be made, it is 

 probable, to the end of time ; so that whoever flat- 

 ters himself that he can produce a perfect work in 

 this department will be miserably disappointed. The 

 utmost that can reasonably be expected from natu- 

 ralists, is to keep pace with the progress of know- 

 ledge ; and this the authors have used their best 

 diligence to accomplish. Every new^ year since they 

 took the subject in hand, up to the very time when 

 the first sheets were sent to the press, numerous 

 corrections and alterations have suggested them- 

 selves ; and thus they are persuaded it would be 

 were they to double the period of delay prescribed 

 by Horace. But Poetry and Natural History are on 

 a different footing ; and though an author can plead 

 little excuse for giving his verses to the world while 

 he sees it possible to polish them to higher excel- 

 lence, the naturalist, if he wishes to promote the 

 extension of his science, must be content to submit 

 his performances to the public disfigured by nu- 

 merous imperfections. 



