194 Scientific Proceedings, Royal Dublin Society. 



chamber, which was attached by a pipe to a powerful hydraulic 

 pump, which was capable of exerting a pressure of 300 atmo- 

 spheres. The small screen of barium platino-cyanide could be 

 seen through the quartz window phosphorescing brilliantly. The 

 pressure was then suddenly raised to 300 atmospheres, but not the 

 slightest diminution in the brilliancy of the screen could be 

 detected. The experiment was repeated several times with the 

 same result. 



Taking the specific gravity of rock at 2*5, the pressure exerted 

 was equal to that of 3600 feet of rock, which was probably greater 

 than any pressure to which the pitchblende had been subjected 

 since the rocks of Bohemia assumed their present conformation. 



From this experiment it seems most probable that the radium 

 has been giving off its energy for untold ages, and the mystery 

 still remains as to the source of the energy. Is it from atomic 

 change, or is it from surrounding space ? 



I am indebted to Mr. E. J. Moss for assistance in carrying out 

 this experiment. 



