Hypothesis of the Internal Fluidity of the Earth. 133 
more intense. The cubic contents of the earth amount to 
about 259,431,755,889 
miles, from which deducting that part of 
which the temperature is under 212°, 295,219,500 
miles, we have 259,136,536,389 
cubic miles of a temperature exceeding that of boiling water. 
From this it appears that the proportion which that part of 
the globe of which the temperature is below 212° bears to 
that possessed of higher degrees of heat, is as one to 878 
nearly. In like manner, the proportion which that part of 
the earth's mass possessed of a temperature of 752° or under 
bears to that of a higher temperature, is as one to 218. 
2. Cast iron fuses at about 2786° Fahr. Taking the pre- 
sent mean temperature of the whole surface of the earth at 
67°, the temperature of molten cast iron will, according to the 
foregoing assumptions, be reached at a depth of 40,785 yards, 
or 23'173 miles. This, then, would be the average thickness 
of the solid crust of the earth at present, supposing the 
materials of which it consists to possess about the same 
degree of fusibility as cast iron- By descending 45,000 
yards, or 25-56 miles, we should experience an increase of 
heat amounting to 3000° Fahr. At such a depth the tem- 
perature (3067°) would probably be sufficient to hold in a 
state of fusion by far the greater part of such substances as 
there exist, unless, which is by no means probable, they are 
much more infusible than the great bulk of the substances 
composing that part of the crust with which we are more 
intimately acquainted. 
3. Since (by hypothesis) the whole earth was at one time 
in a molten state, let us assume that the surface temperature 
was then 3067° or 3000° more than the mean surface tem- 
perature at present. In order, then, that the crust should be 
cooled down to its present state, it would require to part 
with an amount of heat equal to 3-^° or 1500° upon the 
whole, the upper surface losing 3000° of heat, and the lower 
or interior surface nil. 
4. The contraction resulting from refrigeration would 
necessarily shorten the earth's radius. To ascertain the 
amountof such shortening, let it be granted that the materials 
