KELVIN 201 



could come from a store of energy lost out of a gramme 

 of radium in ten thousand hours. It seemed to him, 

 therefore, absolutely certain that if emission of heat at 

 the rate of 90 calories per gramme per hour, found by 

 Curie at ordinary temperatures, or even at the rate of 38, 

 found by Sir James Dewar and Monsieur Curie from a 

 specimen of radium at the temperature of liquid oxygen, 

 could go on for month after month, energy must somehow 

 be supplied from without, to give the energy of the heat 

 getting into the material of the calorimetric apparatus. 

 It was suggested that somehow ethereal waves might 

 supply energy to the radium while it was giving out heat 

 to the ponderable matter around it. Think of a piece of 

 black cloth hermetically sealed in a glass case and sunk 

 in a glass vessel of water exposed to the sun, and think 

 of another equal and similar glass case containing white 

 cloth submerged in an equal and similar glass vessel of 

 water, similarly exposed to the sun. The water in the 

 former glass vessel would be kept very sensibly warmer 

 than the water in the latter. This was analogous to 

 Curie's first experiment, in which he found the tempera- 

 ture of a thermometer with a little tube containing radium 

 kept beside its bulb in a little bag of soft material to be 

 permanently about 2 C. higher than that of another equal 

 and similar thermometer, similarly packed with a little 

 glass tube not containing radium beside its bulb. By 

 changing the water in the two glass vessels a calorimetric 



