674 T. C. CHAMBERLIN 
to render the hypothesis improbable in the present state of 
knowledge. 
The competency of self compression to generate the internal 
heat of the earth is also a critical question already touched upon. 
Estimates made by different methods seem to give an ample 
supply. Thesafest seemingly is that of Mr. Moulton who simply 
computed the energy that would be required to lft the matter 
of a homogeneous earth of 5.6 sp. gr. against gravity alone to 
such a height as to give the whole a uniform specific gravity of 
3.5. This is more than the present specific gravity of the moon 
and is obviously extremely conservative. The fall of this matter 
was found capable of raising the whole mass (specific heat being 
taken at the over-figure of .2), to 6560° C., or about four times 
the average melting, pointyot =rock) at) the ‘sunacesa) tacme 
original specific gravity be taken at 2. on a gross average, which 
seems much more probable than 3.5, when the supposed loose 
state of aggregation is taken into account, the possible tempera- 
ture, if all the potential energy were converted into heat and 
retained, would exceed 13,000°. A portion of the energy might 
take other forms than heat and a portion would be lost concur- 
rently, but as the heat was generated in the interior and must 
have been conducted to the surface very slowly, the secular loss 
must have been of the conservative order. On the other hand, 
tidal friction and possibly chemical action would add to the 
interior heat and more or less offset these sources of loss. On 
the whole, therefore, self condensation seems a competent source 
of internal heat unless the rate of aggregation was excessively 
slow. 
Although aside from my central purpose, it may be remarked 
that the recognition of a progressive self-condensation of the 
earth from a loose aggregation to a more dense one by a pro- 
longed and still incomplete process presumes a degree and 
quality of shrinkage peculiarly suited to explain the inequalities 
of the earth’s surface. An explanation must be found not only 
for the mountainous wrinklings of the crust in post-Cambrian 
times and the great crumplings and crushings of the Archean 
