PREFACE. xi 



phenomenon of Phosphorescence in dead animal 

 substances, and the emission of light by living 

 animals. 



The fourth division comprises some historical 

 notes upon the subject, and the theory by which 

 I have endeavoured to account for the various 

 phenomena to which the attention of the reader 

 is called in the previous chapters. I have pur- 

 posely placed my theoretical considerations in 

 this section, as they will thus have a better 

 chance of fair appreciation than if their elements 

 had been dispersed throughout the work, ap- 

 pended to every isolated fact or experiment as 

 mentioned or described. 



