VOLCANOS AND RADIOACTIVITY 549 



Mr. Boltwood, of New Haven, has devoted considerable attention to 

 the study of radioactivity in mineral springs and finds that many of 

 the waters of America contain radium emanation. 



It does not appear that any extensive or systematic investigation 

 of the emanations of active volcanos and volcanic gases has been hith- 

 erto made. The only one I can discover is the observation of Rausch 

 von Trauenberg on the crater Vesuvius. The gases from that orifice 

 produced marked ionization and a prompt discharge of the leaves of 

 the electroscope. The subject, however, needs thorough investigation 

 at many other volcanic vents. 



The general result of the investigation, so far as it has gone, has 

 been to make clear the fact that the amount of radioactivity in the 

 earth much exceeds the amount which is necessary, so far as the heat 

 generated by it is concerned, to compensate the loss of heat by con- 

 duction and radiation. In fact, it appears that the thermal condition 

 at present is one of continual increase of internal temperature of a 

 large portion of the earth, or is so in part ; or else, is one of equilibrium 

 between loss and gain. Undoubtedly the amount of radioaction varies 

 somewhat widely in different portions of the earth's interior, in some 

 portions permitting a loss of heat, in others permitting a gain. And 

 when there is a gain, it may proceed in the portions near the surface 

 so far as to liquefy the rocks, and thus furnish all the conditions neces- 

 sary to volcanic eruptions. 



One of the problems at present unsolved is whence comes this radio- 

 active material, and what maintains its activity? For the most part, 

 it gives us the characteristics of radium and in smaller degree those of 

 thorium and uranium. The action of actinium has not yet been suffi- 

 ciently pronounced to be recognized. Polonium is believed to be one 

 of the transitional forms of radium. No other radioactive substances 

 are yet known. The most important one thus far identified is radium. 

 But the life and activity of radium is, from a geological standpoint, 

 very brief. According to Professor Rutherford, and he is sustained by 

 nearly all other physigists, radium is half consumed in a period of 

 1,300 years. In 13,000 years only the thousandth part of what now 

 exists will be left, and in 26,000 years, only the millionth part will 

 remain. Quite independently of geological reasons, the belief has been 

 that radium is generated as the product of decay of some other element, 

 and that the amount of it in nature is sensibly constant. It is gen- 

 erated as rapidly as it decays. The parent element from which it may 

 be derived is not yet decided, but there are some who suspect it to be 

 uranium, which has immensely long life. It requires nearly 120,000,- 

 000 years to be half consumed by its own decay. 



But we are not interested in pursuing and trying to test these un- 

 solved problems. It is enough for us that radioaction exists in suffi- 



