896 



SCIENCE. 



[N. S. Vol. IX. No. 235.. 



possibilities of the case. Tlie metal is sup- 

 posed to have been originally scattered 

 uniformly through the rock material in 

 meteoric fashion, and to have gathered 

 thence to the center, forcing the rock mate- 

 rial outwards so far as necessary. The heat 

 produced, Mr. Moulton found to be suffi- 

 cient to raise the temperature of the whole 

 earth (specific heat taken at .2) more than 

 3,000° C. The magnitude of this result is 

 sufficient to require the careful considera- 

 tion of the potential element unless the 

 whole hypothesis can be set aside. It is 

 large enough to cast the gravest doubt on 

 any conclusion based on the rate of a sup- 

 posed decline of internal temperature. Com- 

 plete readjustment of the interior matter, 

 however, is not postulated under the slow- 

 accretion hypothesis. It is only assumed 

 that a slow readjustment has been in 

 progress throughout the geological ages 

 and still is in progress, and that this has 

 changed a certain amount of potential en- 

 ergy into sensible heat and that this heat 

 has contributed to the maintenance of the 

 internal temperature of the earth. 



But there are in addition, incidental fac- 

 tors which enter effectively into the case. 

 The gravitative readjustment of the hete- 

 rogeneous interior material is presumed to 

 have taken place by the descent of the me- 

 tallic and other heavier materials toward 

 the center and the reciprocal ascent of 

 lighter materials from the central region 

 toward the surface, this being accomplished 

 in various ways, the most declared of which 

 has its superficial manifestation in volcanic 

 action. Now, this process of vertical trans- 

 fer, beside developing heat in proportion to 

 the work done, as above indicated, also 

 incidentally brings the hotter material of 

 the interior toward the surface and thus in- 

 creases the subsurfieial temperature. It is 

 a species of slow convection. This convec- 

 tion is in no radical sense different from 

 that which is supposed to have taken place 



in the liquid earth, save that it was delayed 

 so that the heat is available within the life 

 era of the earth, instead of being brought to 

 the surface and dissipated in the prezoic 

 hot stage, when it was a barrier to the 

 existence of life instead of an aid. 



Again, in the liquid earth there were the 

 best imaginable conditions for the inter- 

 mixture of the earth constitutents and for 

 the formation of such chemical and mineral 

 combinations as best accorded with the 

 high pressures of the interior. In the 

 heterogeneous solid earth, on the other 

 hand, such combinations were restrained 

 and delayed and have been able to take 

 place only slowly throughout the secular 

 intermingling of the internal material. It, 

 therefore, hypothetically follows that 

 throughout geological ages, as the internal 

 material was able slowly to readjust itself, 

 new chemical and mineral combinations 

 become possible. These combinations would 

 be controlled by the high pressure in 

 the interest of maximum density, and of 

 hypothetically possible mineral combina- 

 tions, only those would form which gave 

 the higher density.* Thus a slow process 

 of recrystallization in the interest of greater 

 density would be in progress throughout 

 the ages. This denser crystallization would 

 set free heat. It would furthermore permit 

 the shrinkage of the whole mass and the 

 consequent intensification of its self-gravi- 

 tation and this would in turn result in 

 further development of heat. This large 

 possible shi'inkage meets the demands of 

 geological phenomena at a point where the 

 liquid earth has been felt to conspicuously 

 fail. The losses of heat from the earth, as 

 computed by Lord Kelvin and other au- 

 thorities, and the shrinkage resulting there- 

 from have long been held to be quite 

 incompetent to produce the observed in- 

 equalities. Their incompetence is now 



* Professor C. R. Van Hise has worked this out 

 elaborately in manuscript not yet published. 



