This doctrine has for a long time been accepted by geologists as a fundamental principle of their science, Their researches not corroborate this theory, but supply evidence which, coupled with the results of observation as to movements now going on in the earth's crust, shows that the process of cooling and consolidation is still in operation.
The phenomena of volcanoes would appear to afford direct evidence of the interior of the earth being still in a state of intense heat. In a paper submitted to the Royal Society in 1874, Mr Robt. Mallet attributed the heat by which volcanic eruptions are produced to the effect of friction resulting from the crushing of solid rocks in the cooled surface, This view had not met with much acceptance; but, as Mr. Mallet accounted for the crushing of the crust by the contraction of the interior in the process of cooling, his theory was not inconsistent with the general theory of a cooling earth.
The undulatory movement of the earth's crust, shown by the elevation and depression of the surface, is conclusive evidence that the interior of the earth is not solid. There is abundant evidence of such movements in former geological periods, and at the present time. In the Malvern area a great part of the older rocky have sunk, and new red deposits have taken their place. At Swindon, in Wiltshire, the quarries disclose the remains of an old land surface, which first sunk and became covered with deposits of the cretaceous sea, and was then re-elevated for the enjoyment of terrestrial beings. The Suffolk coast shows similar movements in recent geological tines. Sir C. Lyell, Professor Ramsay, and other authorities testify to similar movements in recent times in Africa, South America, Northern Asia, British Columbia, and the Pacific, and particularly to the elevation of Sweden and the Baltic, now progressing at the rate of 2½ feet in a century.
At a recent meeting of the Geological Society, Captain Fielden, the Naturalist to the recent English North Polar Expedition, stated that at the present time the coasts of Greenland and Grinnell Land are steadily rising from the sea. These movements prove conclusively that the earth is not yet solid. They would be explained, if the garth consisted of a mass of mixed substances, such us we are acquainted with as forming its crust. still for the most part in that viscid or yielding condition, which we know that they assume when passing from the molten to the solid state in cooling, such for instance as lava, glass, iron, basalt, &c.
Can the earth’s pristine heat be still retained in it? Assuming that it was once heated, its heat could only escape through the crust. If the crust consisted of absolutely non-conductive materials it would never lose its heat. The crust is not of such a character, but the materials which form its bulk are slow conductors. The escape of heat would become slower as the crust thickened.
Observations of underground temperature show that the heat increases at the rate of one degree Fah. for every 60 feet. This gives a temperature of 2,500 F. at about thirty miles from the surface. At such a temperature lava world be as liquid as water. Pressure may condense
