264 C. E. BUTTON 



possible for water vapor to lift its covering and force a way to the surface, 

 unless it had a temperature greatly exceeding 1,200° C. It would 

 have to be heated to a considerably higher temperature to do it. But 

 with increasing temperature the heat is conducted awaymore and more 

 rapidly, until the loss of heat is equal to the quantity generated and 

 thereafter there is no increase of temperature. The generation of 

 radioactive heat is a slow process, and the only method of its escape is 

 by conduction away from the radioactive source. The rate of heat 

 generation is constant and independent of the temperature, but the rate 

 of loss increases rapidly with the temperature. Ultimately, as the 

 temperature rises, a point would be reached at which the loss of heat 

 becomes equal to the gain. 



If an eruption from a deep source, say five or six miles, were to occur, 

 we should expect that the temperature of the lava would be very high — 

 probably a white heat — and that its mass would be very great. Its 

 consequences might be disastrous beyond all precedent. 



That volcanism is caused by the generation of heat near the surface 

 was a behef which I expressed over twenty years ago in a chapter of the 

 work on Hawaiian Volcanos. Long study of the volcanic problem,, 

 in which every other theory failed and went to pieces under criticism,, 

 and this alone not only survived, but grew more probable and in accord- 

 ance with the facts, led me to the hazardous step of venturing to express- 

 it. At that time no cause could be cited for the increase of heat, and 

 the proposition met with no response — and, no doubt, justly. Geolo- 

 gists continued to look for the explanation of volcanoes in the gradu- 

 ally waning remnants of the earth's internal heat. Within the last 

 five or six years, however, physical science has made discoveries of a. 

 wonderful nature, which open a new field — indeed, a new world — in 

 our views of the constitution of matter, and may throw a flood of hght 

 on the very subject of our inquiry. 



The subject of radioactivity is so new and so surprising that it has 

 had time only to estabhsh a very few of the fundamental principles 

 which he at the basis of it. But so hotly is the matter pursued by many 

 of the ablest speciahsts that each year shows a large increase in our 

 knowledge. As this is famihar to all physicists, I shall allude here 

 briefly only to such as are essential to our discussion. We have to 

 regret that some of the most fundamental questions concerning radio- 



