ST CLEAVAGE, ETC. 31 



observed. The rare mineral called samarskite (nio- 

 bate of iron, of uranium, and of yttria) presents the 

 same phenomenon to a less degree. 



Oxide of molybdenum (MoO) is obtained by 

 heating the hydrate of this oxide in vacuo : 

 when the water is all evaporated, the dry oxide re- 

 maining appears as if on fire; the anhydrous or 

 dry oxide is then completely formed. 



According to Berzelius antimoniate of copper 

 becomes luminous when heated, and changes its 

 chemical nature. Something similar has been ob- 

 served with phosphate of magnesia. 



About fifteen years ago, M. Scheerer showed 

 that the density of gadolinite (which, like samar- 

 skite, contains no water) increases during the 

 phosphoric radiation ; the density of the mineral is 

 greater after the experiment than before. M. H. 

 Rose has confirmed this fact anew, and has shown 

 at the same time, that with samarskite the con- 

 trary is observed : the density diminishes. These 

 observations alone prove that a molecular change 

 takes place during the emission of light. 



H. Rose has also confirmed the fact announced 

 some time ago by Regnault as an hypothesis, via. 

 that the luminous phenomenon which occurs 

 when the substances above alluded to suddenly 

 change their state, is accompanied by an imme- 

 diate change in their specific heat. Thus, the 

 specific heat of gadolinite diminishes one-four- 



