Analytical Abstracts of Current 

 Literatures 



The Age of the Earth, by Clarence King. (American Journal of 

 Science, vol. 45, Jan. 1893, pp. 1-20, with 2 Plates). 



The object of Mr. King's paper is to advance the method of determining 

 the earth's age which was employed by Lord Kelvin (Sir William Thomson), 

 and which was based on a consideration of its probable rate of refrigeration, 

 by appl3nng to it new criteria. The criteria are derived from the tidal 

 effective rigidity of the earth, and the further argument for rigidity based 

 upon the periodic variation of latitude, and also from the researches of Dr. 

 Carl Baru^ upon the latent heat of fusion of the rock diabase, and upon its 

 specific heats when melted and solid, and upon its volume expansion between 

 the solid and melted state. This rock was considered to represent the pro- 

 bable density and composition of the surface .03 or .04 of the earth's radius. 



The two principal conditions within the interior of the earth upon which 

 physical state and all purely physical reaction of the specific materials depend, 

 being the distribution from center to surface of pressure and heat, Mr. King 

 points out the relative values of earth - pressures deduced from Laplace's law, 

 and two hypothetical cases of earth - temperatures. These are expressed by a 

 diagram which shows that the temperatures maintain an almost maximum 

 value from within .05 of radius of the surface to the center of the earth, while 

 pressure increases steadily throughout the entire radius. Near the surface the 

 rate of increase of heat is greater than that of pressure, and hence its effect 

 is to overcome the results of pressure. But this relation obtains only for earth - 

 depths of 200 miles for an earth of the Kelvin assumption. Below this the 

 relations are completely reversed. 



The results of Barus's researches furnish the means of fixing the melting 

 points of diabase at pressures corresponding to increasing depth within the 

 earth. These points fall in a straight line when plotted on a chart in which the 

 coordinate axes represent temperatures and parts of the earth's radius. By 

 plotting on the same chart curves expressing the temperature gradients of the 

 earth for different assumptions regarding the initial excess of heat and period 

 of cooling, it is possible to determine the extent of the couche which must remain 

 fused in certain cases, and also the temperature gradient at the surface of the 



'Abstracts in this number are prepared by Joseph P. Iddings, J. A. Bownocker, 

 Henry B. Kummel, Chas. E. Peet. 



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