BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 26, pp. 171-204 March 31, 1915 



ISOSTASY AND EADIOACTIVITY ' 



PRESIDENTIAL ADDRESS BY GEORGE F. BECKER 



{Read before the Socieltj December 2'.), IDlJf) 



CONTENTS 



Page 



Introductory ITl 



Premonitions of isostasy 172 



Direct investigations of isostiisy 178 



Discussion of isostasy 185 



Note on epeirogeuy 188 



Recent advances in radiology 189 



On tlie earth's radiation 195 



I 'Onclusions -02 



Introductory 



It is the purpose of this paper to point out some apparent discrepancies 

 between the observations of geodesists on isostasy and the inferences 

 which some radiologists have drawn as to the great age of certain speci- 

 mens of minerals. It seems well to begin by reviewing the results of 

 isostatic investigations, in order to estimate the degree of confidence to 

 which they are entitled; and recent advances in radiology demand similar 

 attention. 



Correlation of these widely distinct researches is possible because it 

 happens that the emission of heat by a globe whose excess temperature is 

 due solely to radioactivity obeys Fourier's law exactly as does that emitted 

 by a hot but radioinactive 'globe. It is tims easy to plot the distribution 

 of temperature in a globe which at the consistentior status had a high 

 temperature due in part to radioactivity and in part to compression, the 

 diagram being strictly analogous to that given l)y Kelvin for a cooling 

 globe.^ By trial and error it is possible to obtain an approximate answer 

 to the question whether in the present state of science it can be admitted 

 that the greater part of the heat radiated 1)\ the earth is of radioactive 

 origin ;iiiil wliother approximately complete isostatic compensation ;it such 



' Manuscript receivod by Hio Socrot.ii-y of (ho Society Decpmhpr 20, 1014. 



By reason of illness, Dr. Becker was unable to present his paper in person. 

 2 Nat. Phil., part 2, p. 477. 



XIII— Bull. Gkol. Soc. Am., Vol. 26, 1914 (171) 



