Clarence King — Age of the Earth. 9 



the chart is divided into two areas by the line, that above it 

 representing fluidity, and that below, solidity. For a diabase 

 earth to have been wholly melted an initial excess of 76,200° 

 C. wonld be required. Obviously any earth having an initial 

 excess of less than the surface melting point 1,170° C would 

 have been always completely solid. Any initial excess above 

 that figure and below 76,200° C. requires at the moment before 

 refrigeration began, a solid nucleus and a fused zone above it 

 extending to the surface, and the lower the initial excess the 

 larger the solid nucleus of compression and shallower the 

 initial couche of surface fusion. Knowing the law of the 

 rise of the fusion-point it is a simple matter of computation 

 to determine, for any assumed initial excess, exactly the radial 

 value of the original solid nucleus and of the original super- 

 natant fluid couche. For the region covered by the chart 

 these values may be directly scaled off. 



Fourier's equation enables us to go further and assuming 

 that refrigeration is the result of conduction alone to determine 

 the temperature distribution for any given period of refrigera- 

 tion, and what is of particular geological interest the rate at 

 which the fused couche is encroached upon by an overlying 

 superficial crust of congelation, and the existence, depth, tem- 

 perature and pressure differences of any residual fluid couche 

 between the upper and lower solids. The relation, therefore, 

 of any temperature gradient to the diabase line offers an im- 

 mediate test of its admissibility as a probable case. Any tem- 

 perature gradient that in passing across the area of the chart 

 from below to the surface intersects the diabase line must in 

 reaching the low temperatures of the surface intersect it again, 

 and the zone included between the pair of points of intersec- 

 tion being above the line, and hence for that interval of 

 radius above the fusion temperatures, must be a melted 

 shell, and as on the criterion of solidity the existence of any 

 considerable fusion is precluded, such a case of temperature 

 distribution may be rejected. 



I will now trace the several temperature distributions 

 upon the chart, and note their relations to time and solidity, 

 beginning with the family delineated in continuous lines 

 (surface rate 50 - 6 ft. to 1° Fahr.). Line h, the gradient 

 of Kelvin, 3,900° C. initial excess, lOOxlO 6 years secular 

 cooling, is seen to enter the chart from the lower regions, 

 maintaining even to the shallow depth of 226 miles from 

 the surface, practically, its original maximum temperature. 

 From the center of the earth up to this point it has remained 

 in the initial solid of compression. At the depth noted it 

 intersects the diabase line and passes into fusion. Since almost 

 the full initial temperature is maintained up to its intersection, 



