NO. 6 AGE OF TTTE EARTH BECKER 5 



portion of the large mass of data accumulated during the past decade has 

 been determined at our suggestion, though most of the hydrological work of 

 the U. S. G-eological Survey, including the very numerous analyses executed 

 under the charge of Mr. E. B. Dole, has formed part of a systematic 

 effort to develop the mineral resources of the Commonwealth. In pur- 

 suance of our common aim Mr. Clarke has now completed a review of all 

 available data, not only for the United States but for the world, and his 

 paper is published by the Smithsonian Institution under the title, " A 

 Preliminary Study of Chemical Denudation." ' His results form the basis 

 of a discussion of the age of the ocean which will be presented below. 



Ivelvin in 1862 first discussed the age of the earth considered as a cool- 

 ing body. His results were for some years received with sorrow and indig- 

 nation by most geologists and especially by evolutionists, who then desired 

 unlimited time in whicli to effect the development of species. More 

 mature study has convinced the scientific world that there is no necessary 

 discrepancy between Kelvin's 20 to 400 million years, with a probable 98 

 million, and the conclusions of geologists or paleontologists. In 1893 

 Clarence King, with the aid of Mr. Carl Barus, introduced the important 

 criterion of tidal stability and reached the conclusion that 24: million 

 years best represented the conditions.' This result was accepted by Kelvin 

 in 1897' and he then placed the limits at 20 and 40 million years. The 

 earths considered had uniform initial temperatures. In 1908 I showed 

 that such a distribution of temperature necessarily involved a prolonged 

 period of tidal instability and discussed a globe the initial temperature of 

 the outer shell of which increased in simple proportion to the distance 

 from the surface.^ 



Only Sir George H. Darwin has discussed the age of the earth from a 

 purely astronomical point of view. From his theory of the earth-moon 

 system he derived an estimate of more than 56 million years which for a 

 long time stood rather alone between groups of higher and lower figures. 



In the succeeding pages will be found my discussion of Mr. Clarke's 

 data and also a revised edition of my paper on the age of the earth as 

 determined from refrigeration. The two arguments accord remarkably 

 well. 



' Smithsonian Miscellaneous Collections, vol. 56, No. 5, 1910. 

 - Amer. Jour. Sci., vol. 45, 1893, p. 1. 

 ■'Trans. Victoria Inst., vol. S^, 1899, p. 11. 

 * Science, vol. 27, 1008, p. 227. 



