1884.] On the Evidence that the Earth's Interior is Solid. 679 
the earth’s materials contract or expand on solidification ? Mous- 
son experimented further on the action of water according to 
Thomson’s law, and showed that it required enormous 
pressure to lower the melting point of ice a few degrees! 
So far then as any conclusion can be drawn from these experi- 
ments, it would show that the pressure must increase to an enor- 
mous amount to keep pace with the supposed increase of heat— 
à pressure that the earth’s specific gravity negatives, 
It can well be claimed that the known rate of the elevation of 
temperature, as the interior is approached, far surpasses the known 
fate of change of the fusion point by pressure in the few cases 
investigated. 
David Forbes has further pointed out that, since the substances 
mainly experimented upon by Hopkins and Bunsen are not, ex- 
cept sulphur, components of the earth, experiments made with 
do not necessarily apply to the materials of which the 
farth is composed. He also suggested that if the pressure is 
raised to great heights the reverse may be true regarding the 
effect of pressure on the melting point—it may lower instead of 
false it, He also thought that we should look rather at the results 
obtained by Hopkins from the alloys instead of those from the 
Wax, etc? 
In discussing the state of the earth’s interior, Dr. T. Sterry 
Hunt advanced the argument that the material of the earth, when 
M its former fused state, would solidify from the center on 
account of the congealed mass being much heavier than the 
ud: “We may say in a few words that the process of cooling 
à mass like this would be just like the cooling of a great bath 
metal or of sulphur; in other words, the condensation or con- 
would commence at the center and extend outward to- 
Ward the Surface, so that the temperature of the center would 
therefore be the temperature of congelation.”® 
David F orbes, in reply to Dr. Hunt’s argument, very perti- 
remarked that no one “had ever seen a mass of metal or 
sg crystallize or solidify in the interior first, since the inte- 
of such masses, it is well known, remain liquid after the 
1 
: Rien > TAR 1858, cv, 161-174; Everett’s Deschanel’s Natural 
Pry, & x 2, PP. 312, 313; 1883, pp. 331, 332- 
t Geot a €v. „1869, vIr, 121-130; Geol. Mag., 1867 (1), IV, 431-444. 
S26 1877 (1), 1, 357-369. 
