MOVEMENTS AND DEFORMATIONS OF THE EARTH'S BODY. 565 



increase of the density varies as the square root of the increase of the 

 pressure. This law gives a distribution of density that accords fairly 

 well with the phenomena of precession of the equinoxes, which require 

 that the higher densities of the interior shall be distributed in certain 

 proportions between the center and the equatorial protuberance whose 

 attraction by the sun and moon causes precession. The increases in 

 pressure, density, and temperature have been computed as follows by 

 Mr. A. C. Lunn/ the average specific gravity of the earth being taken at 

 5.6, the surface specific gravity at 2.8, and the specific heat at .2. 



The temperatures are shown graphically in Fig. 452, in which the 

 curves of pressure and density are also given. The nature of the curve 

 of temperature is such that, if the thermometric conductivity of the 

 material is uniform at all depths, the temperature will fall in the deeper 

 portions and rise in the outer ones, excluding the surface portions subject 

 to outside cooling. The curve indicates that the rising temperature 

 would affect somewhat more than 800 miles of the outer part of the 

 spheroid, or about half its volume, i.e. the inner half during the initial 

 period had a falling temperature and the outer half, except the imme- 

 diate surface, a rising temperature. This introduces a very singular 

 feature into the problem, for the outer zone must shrink to fit the inner 

 portion that is losing heat, while its o^vn material is expanding because 

 of its increase of temperature. A double distortional effect must result.^ 

 If the conductivity of the dense interior is greater than that of the outer 

 parts, the effect is intensified. The redistribution of heat resulting 

 from this unequal flowage would in time change the curve so that more 

 nearly equal flowage would result. It would probably take a very 

 long period for this to be effected, on account of the very slow con- 

 ductivity of rock. 



The accretion hypothesis assumes that, during the growth of the 

 earth, large amounts of heat were carried by volcanic action from deeper 



^ The pressures and densities here given are essentially the same as those previously 

 worked out by others and already published. The temperatures are the results of 

 recent preliminary compulaions made under the auspices ot the Carnegie Institution, 

 and are subject to change on further study. They are based on the assumption that 

 the increase in density is due to compression. They are in general accord with the 

 results previously reached by Dr. F. R. Moulton (see "A Group of Hypotheses Bearing 

 on Climatic Changes," by T. C. ChamberUn, Jour, of Geol., 1897, p. 674). The Rev. O. 

 Fisher, in the Am. Jour, of Sci., 1901, p. 420, gives much higher results. 



2 Attention was called to this feature by Chamberlin in a paper before the Geol. 

 Soc. of Am. at Rochester, December, 1901. 



