420 0. Fisher — Rival Theories of Cosmogony. 



result, that the pressure at the depth where the density is p is 

 equal to 5 '9 X 10 7 (p 2 - s'). 



If' we accept Laplace's law, this expresses a fact, whether the 

 increase of density is due to condensation by pressure or to 

 increased density in the intrinsic nature of the matter. But if 

 we assume that the increase of density is caused solely by the 

 pressure, then the above relation gives the amount of pressure 

 which would reduce matter of density s to matter of density 

 p under the circumstances existing within the earth. It will 

 therefore remain true if the matter changes its state from solid 

 to liquid, and from liquid to gas. If, for instance, we wished 

 to apply a pressure which would reduce surface rock to the den- 

 sity 3, it ought to be 5*9 X 10 7 (9 - 2*75 2 ) = 8-481 X 10 7 pounds 

 per square foot, supposing no heat be allowed to escape. If the 

 experiment could be made, it would afford a test of the truth 

 or otherwise of the present hypothesis. 



When we know the relation between the pressure and the 

 condensation which it would produce, it is feasible to estimate 

 the heat which would be generated, and also the temperature, 

 provided we assume the specific heat of the substance, which 

 for surface rock has been determined. For instance, at the 

 depth of O'l of the radius, or about 400 miles deep, where the 

 density would be 3*88, the temperature produced by condensa- 

 tion would be 1-2608 X 10 b Fahr., or 7'0044 X 10 4 Cent., while 

 at the center the figures would reach 2*7756 X 10 6 Fahr., or 

 1-0242 X 10* Cent. It seems at any rate that the meteoric 

 theory would not fall short of accounting for temperatures as 

 high as might be desired. It must at the same time be remem- 

 bered that much of this heat would not be called into exis- 

 tence until the substance into which it was, as it were, being 

 squeezed, had already been deeply buried under a badly con- 

 ducting covering, so that the escape of the heat would not 

 take place as fast as it was generated, as would probably be the 

 case with heat generated at the surface by impacts. Thus the 

 hypothesis that the present high internal temperatures are due 

 to compression seems quite admissible. 



We may compare the above named temperatures with some 

 that are known. Acheson, for instance, obtains 6500° Fahr. in 

 his Carborundum electric furnace, and 3300° Fahr. has been 

 obtained by the oxyhydrogen flame. These temperatures are 

 contemptible compared with those mentioned above. The 

 Hon. Clarence King, prolonging Dr. Barus' line* for the melt- 

 ing point of diabase (which is 1170° C. at the earth's surface) 

 to the earth's center, gives the temperature 76000° Cent., which 

 is of the same order of magnitude as condensation would pro- 

 duce at only 400 miles depth. 



* This Journal, Jan., 1893, p. 1. 



