Clarence King — Age of the Earth. 



11 



For those whose interest centers in earths of great age 

 and high temperature, gradient a is given, initial excess 

 7,800° C. and 400xl0 6 years secular cooling. This has not 

 been projected to the deep, but would not reach solidity until 

 over 1, 500x10 s years, a truly uniformitarian specimen. 



Turning now to the family of three gradients in dotted line, 

 computed to conform to the surface rate of 75 feet to 1° 

 Fahr., the first, g is seen to be of the same initial excess 

 as the Kelvin 3,900° C. line. In spite of its long cooling even 

 after 237x10" years it is still very far from solidity. Of the 

 original fluid couch e of 226 miles, only about 60 miles has been 

 congealed into crust, 166 miles remaining fused. 



Gradient h, initial excess 2,560° C, and a 100x10 s years re- 

 frigeration has an original fluid couche of 120 miles with 

 a present crust of 56 miles and an existing residual couche of 

 fusion of 64 miles, a case also inadmissible from the point of 

 view of instability. 



Gradient i, initial excess 1,760° C. (platinum melting point), 

 and 46x10" years of cooling, had originally a 53-mile surface 

 couche of fusion which has long since passed into solidity. 

 The following table sums up the condition of all the gradients 

 as to initial excess, initial depth of surface fusion, time of cool- 

 ing, thickness of crust congealed and present residual couche 

 of fusion. 



Table 6. — Liquid Solid Conditions for Diabase Earth. 

 A. — Gradients having the surface rate of 506 to 1° Fahr. 



Initial 

 excess. 



Initial depth 



of surface 



fusion. 



Time of 

 cooling. 





Thickness 



of crust 



concealed. 





Residua] 



couche of 



fusion. 



°C. 



Miles. 



Tears. 





Miles. 





Miles. 



3900 



226 



lOOxlO 6 





26 





200 . 



1950 



66 



15xl0 6 





32 





33 



1741 



53 



20xl0 6 



crust 



and nucleus united 



1230 



6 



10x10 s 



u 





u 







B. — Gradients having the surface rate of 75 feet to 1° Fahr. 



3900 226 237x10° 50 166 



2560 120 100x10" 56 64 



1741 53 46xl0 6 crust and nucleus united 



Comparison of gradients of equal initial excess and succes- 

 sively longer periods of secular cooling shows the ratio of their 

 retreat from right to left across the chart or from lower to 

 higher values of depth and time. 



With each augmentation of age the initial tangent defining 

 the surface rate is seen to have declined further and further 

 from the original rate <x, coinciding with and passing first 



