PREFACE. 
THE original sketch of this work appeared for the 
first time in the ‘Journal de Médecine et de 
Pharmacologie, of Brussels, at the commence- 
ment of the year 1858. It was soon after re- 
printed and published anew at Brussels and Paris. 
At the same time, my original paper was repro- 
duced in Belgium, without my knowledge, in the 
‘Revue Populaire des Sciences,’ by M. Husson, 
and in France, in the ‘Ami des Sciences,’ a 
weekly paper, edited by M. Victor Meunier. 
Unknown to me, it was translated also into 
German, by Dr. Miiller, of Berlin, about two 
months after its first appearance; and I have 
since learnt that an Itahan edition was expected 
to appear shortly. 
I was thus convinced that the subject of Phos- 
phorescence deserved to be treated far more ex- 
