MOVEMENTS AND DEFORMATIONS OF THE EARTH'S BODY. 567 



absorbed the necessary heat of liquefaction and began to work their 

 way outward, carrying their heat into higher horizons and temporarily 

 checking the development of more intense stresses in the lower horizons. 

 They thus served to keep the temperature there below the fusion-point 

 of the remaining more refractory substances. Meanwhile the extruded 

 portions were raising the temperatures of the higher horizons into which 

 they were intruded or through which they were forced to pass. There 

 was thus, it is thought, an automatic action that tended to reduce the 

 heat-curve to the fusion-curve. The actual curve of internal tempera- 

 ture may, therefore, he practically the fusion-curve. This is identical mth 

 the curve supposed to arise from solidification by pressure from the 

 center outward under the molten hypothesis, except so far as the two 

 would vary as the result of variations in the distribution of matter, 

 which would not be quite the same under the two hypotheses. The 

 curve of fusion deduced by an extension of the results of Barus' experi- 

 ment has been given. It is necessary to recognize that the rate of rise 

 of the fusion-point may, and ver}^ likely does, change in the deep interior. 

 The curve given represents much higher temperatures in the central 

 parts than those given by Lunn's computations from compression, which 

 seem inherently more probable than the higher ones. 



As astronomical and seismic evidences strongly favor the view that 

 the earth is rigid throughout, they lend support to the view that the 

 interior retains its rigidity by the extrusion of liquid matter practically 

 as fast as it is formed, and that this progressive extrusion adjusts the 

 temperature to that which is consistent with solidity. 



The bearing of this conception becomes evident on consideration. 

 The shrinkage of the earth from loss of heat by conduction and by the 

 extrusion of molten rock, affects the deep interior as well as the more 

 superficial zones. It is even possible that the shrinkage may originate 

 chiefly in the deeper zones. The postulated transfer of fluid rock from 

 the deeper parts to the more superficial ones lessens the heat in the 

 former, and adds to that in the latter. The postulated greater flow 

 of heat from the deeper half to the outer half, than from the latter out- 

 ward, gives a concordant result. If the conductivity of the deeper and 

 denser material is appreciably greater than that of the more superficial 

 and less dense material, as seems probable, this effect is intensified. 

 The distribution of compressibility at the existing state of condensa- 

 tion may possibly be such that more new heat is generated by shrink- 



