346 AGE OF THE EARTH AS AN ABODE PITTED FOR LIFE. 



amount, or a little less than 10,000,000 years; but the effect of pressure 

 on the temperature of solidification must also be taken into account, 

 and Mr. Clarence King, after a careful scrutiny of all the data given 

 him for this purpose by Dr. Barns, concludes that without further 

 experimental data "we have no warrant for extending the earth's age 

 beyond 24,000,000 years." 



19. By an elaborate piece of mathematical bookkeeping I have 

 worked out the problem of the conduction of heat outward from the 

 earth, with specific heat increasing up to the melting point as found 

 by Eiicker and Roberts- Austen and by Barus, but with the conductivity 

 assumed constant; and, by taking into account the augmentation of 

 melting temperature with pressure in a somewhat more complete man- 

 ner than that adopted by Mr. Clarence King, I am not led to differ 

 much from his estimate of 24,000,000 years. But until we know some- 

 thing more than we know at present as to the probable diminution of 

 thermal conductivity with increasing temperature, which would shorten 

 the time since consolidation, it would be quite inadvisable to publish 

 any closer estimate. 



20. All these reckonings of the history of underground heat, the 

 details of which I am sure you do not wish me to put before you at 

 present, are founded on the very sure assumption that the material of 

 our present solid earth all round its surface was at one time a white- 

 hot liquid. The earth is at present losing heat from its surface all round 

 from year to year and century to century. We may dismiss as utterly 

 untenable any supposition such as that a few thousand or a few million 

 years of the present regime in this respect was preceded by a few 

 thousand or a few million years of heating from without. History, 

 guided by science, is bound to find, if possible, an antecedent condition 

 preceding every known state of affairs, whether of dead matter or of 

 living creatures. Unless the earth was created solid and hot out 

 of nothing, the regime of continued loss of heat must have been 

 preceded by molten matter all round the surface. 



21. I have given strong reasons' for believing that immediately 

 before solidification at the surface the interior was solid close up to 

 the surface, except comparatively small portions of lava or melted rock 

 among the solid masses of denser solid rock which had sunk through 

 the liquid, and possibly a somewhat large space around the center 

 occupied by platinum, gold, silver, lead, copper, iron, and other dense 

 metals still remaining liquid under very high pressure. 



22. I wish now to speak to you of depths below the great surface of 

 liquid lava bounding the earth before consolidation, and of mountain 

 heights and ocean depths formed probably a few years after a first 

 emergence of solid rock from the liquid surface (see 24 below), which 

 jiiust have been quickly followed by complete consolidation all round 

 the globe. But I must first ask you to excuse my giving you all my 



' On the Secular Cooling of the Earth, Vol. Ill, Math, and Phys. Papers, ^S^'i 19-33. 



