144 G. F. BECKER RELATIONS OF RADIOACTIVITY TO COSMOGONY 



is unimportant. If, ho-vrever, tlie amount of radioactivity diminisiies 

 with depth, the shell of radioactive matter must be thicker than that 

 computed.®" 



Although the contribution of radioactivitj^ to the total heat of the 

 globe appears to be relatively small, the influence of radioactivity on geo- 

 logical processes may have been great. So far as the action of "mineral- 

 izers" is understood, it -vrould seem that radioactive matter should be 

 extraordinarily efficient. It is hard to see how any chemical or physical 

 reaction could hang fire under the bombardment of a particles, which 

 seems comparable to the explosion of fulminate of mercury. The influence 

 of radium on the crystallization of artificial minerals ought to be studied, 

 and it will be strange if it is not found useful. Mining geologists and 

 petrographers also should endeavor to ascertain whether phenomena 

 hitherto mysterious are not explicable by radioactivity, but they will 

 probably meet with little success until further systematic laboratory re- 

 searches have been made with the especial purpose of elucidating the 

 subject. Unfortunately there seems no hope of this until the funda- 

 mental importance of geophysical researches is more generally appre- 

 ciated. 



SUMIVIAEY 



This paper begins by an attempt to outline in sufficient detail for the 

 use of geologists the magnificent investigations of a small group of 

 physicists on radioactivity. A^Tiile a few matters are still in doubt, these 

 are relatively unimportant to geologists, and it is fully established that 

 radioactivity must be taken into account in estimating the age of the 

 earth as well as in the explanation of geophysical phenomena. 



*• If the heat developed by radioactivity were greatest at the surface, s;ay equal to 

 go, and diminished linearly with depth, vanishing when the depth were <r, then the 

 heat developed per cubic centimeter would be 



' % 



(l_iL) and 4^ = -^ (l--) 

 ^ <r ' dx- k ^ a- ' 



Making the temperature gradient zero when a; = er and the temperature excess, or r, 

 zero at the surface, the equations 



represent the distribution of gradient and temperature. The surface gradient in this 

 case Is 





2k 



and the curvature of the temperature curve is considerably nearer the surface, because 

 in this neighborhood d-v/di- is finite. On the other hand, at the bottom of the radio- 

 active layer d-i/djc:- vanishes. In the case of a cooling globe the curvature of the ex- 

 cess of temperature curve is zero at the surface. 



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