ADVERTISEMENT. 



THE following papers, which were published 

 many years ago in the Transactions of the Royal 

 Society, are now for the first time collected, and 

 republished in a separate volume. 



I have availed myself of the opportunity thus 

 afforded to offer, in the form of notes, some ad- 

 ditional observations, which appear in some in- 

 stances to confirm, while in others they have 

 led me to modify, the conclusions at which I 

 had arrived formerly. 



Having been long engaged in the duties of 

 an arduous profession, I have not had it in my 

 power to continue the pursuit of those physio- 

 logical inquiries to which I was able to devote 

 a considerable portion of my time during the 

 early part of my professional life. However, 



M37S998 



