viii PREFACE. 



tensively than had been done in my "brochure, a 

 mere sketch, which is now out of print ; so that, 

 instead of republishing it with additions,, I have 

 completely remodelled the work, and brought 

 forward in the present volume every case of Phos- 

 phorescence which it has been in my power to 

 obtain (many of which have originated in my own 

 laboratory), after seeking for and studying the 

 phenomenon in the whole domain of Nature. 

 My attention was first called to this extremely 

 interesting class of natural facts by my physical 

 and chemical studies. They have occupied my 

 thoughts for some time past ; and I was the more 

 anxious of treating this subject in extenso, since, 

 up to the present day, it has been impossible to 

 give a satisfactory explanation of phosphoric phe- 

 nomena. 



Phosphorescence, indeed, whether manifested 

 by the glowworm, the Bologna stone, a fungus, 

 or a falling star, is generally looked upon as an 

 unexplained and mysterious production of light. 

 I hope, nevertheless, that I have been able to ex- 

 tricate it a little from the obscurity in which it 

 has hitherto been enveloped. 



In order to appreciate every circumstance con- 



