24 The American Geologist. July. 1894 
formerly accepted melting points of man}' substances, we may 
expect this result for diorite to be reduced also. It therefore 
seems to me that we may assume the temperature of the earth 
at the period of the solidification of the crust to be about 
3,000° F. 
The temperature of the interior would have prevented a 
rapid thickening of this crust. After the crust had formed, 
the heat of the metallic interior would have still been rapidly 
communicated to the outer crust. It must not be forgotten 
that it was not a case of heating a cold crust; but that the 
heat from the interior had simply to continue to How through 
this outer crust. 
The following equation will give the present temperature 
of the earth's interior, as accurately as the factors can be de- 
termined. 
Present temperature of the metallic interior = 
Volume X density x sp. heat X orig. temp. X 62.35.* 
Time of cooling X area of radiating surface X annual loss of heat. 
Substituting in this equation the following values and solv- 
ing, we obtain 468° F. as the present temperature of the earth's 
interior. 
Specific heat of the metallic interior, 0.1. f 
Specific gravity of the metallic interior, 1). 
Time since crust began to form, 60,000,000 years. | 
Assumed average thickness of the crust during this period, 
fifty miles : diameter of the earth, 7,900 miles. 
Temperature of the earth at the time the crust began to 
form, 3,000° F. 
Amount of heat annually flowing through the crust, fort}" 
units of heat from each square foot of the radiating surface 
of the metallic interior. 
In conclusion. I desire to say that I recognize that tin- re- 
sults of my calculation may be criticised, owing to my inabil- 
ity to secure the exact values of the factors in my equation: 
yet that is not the material point of this article, which is in- 
tended to show, to the supporters of the nebular hypothesis of 
'"Wright nf a cubic fool i'i' water in pounds avoirdupois. 
fThis is above the average specific heal of the heavy metals. 
mates of the age of the oldest stratified rocks vary from 10,000,- 
000 to 200,000,000 years. SeeGeikie'sTexl Book of Geology, pp. 56 and 57. 
