PREFACE. 



THE original sketch of this work appeared for the 

 first time in the ' Journal de Medecine 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 

 ' Eevue 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. Muller, of Berlin, about two 

 months after its first appearance; and I have 

 since learnt that an Italian edition was expected 

 to appear shortly. 



I was thus convinced that the subject of Phos- 

 phorescence deserved to be treated far more ex- 



