vill PREFACE. 
tensively than had been done in my brochwre,—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 lght. 
I hope, nevertheless, that I have been able to ex- 
tricate it a little from the obscurity m which it 
has hitherto been enveloped. 
In order to appreciate every circumstance con- 
