The scientific facts upon which this great work was projected, may be stated as follows: It is the opinion of the principal modern geologists, based primarily upon the hypothesis of Kant (that the solar universe was originally an immense mass of incandescent vapor gradually cooled and hardened after being thrown off from the grand central body--afterward elaborated by La Place into the present nebular hypothesis)--that "the globe was once in a state of igneous fusion, and that as its heated mass began to cool, an exterior crust was formed, first very thin, and afterward gradually increasing until it attained its present thickness, which has been variously estimated at from ten to two hundred miles. During the process of gradual refrigeration, some portions of the crust cooled more rapidly than others, and the pressure on the interior igneous mass being unequal, the heated matter or lava burst through the thinner parts, and caused high-peaked mountains; the same cause also producing all volcanic action." The arguments in favor of this doctrine are almost innumerable; these are among the most prominent: _First._ The form of the earth is just that which an igneous liquid mass would assume if thrown into an orbit with an axial revolution similar to that of our earth. Not many years ago Professor Faraday, assisted by Wheatstone, devised a most ingenious apparatus by which, in the laboratory of the Royal Society, he actually was enabled, by injecting a flame into a vacuum, to exhibit visibly all the phenomena of the formation of the solar universe, as contended for by La Place and by Humboldt in his "Cosmos." _Secondly._ It is perfectly well ascertained that heat increases with depth, in all subterranean excavations. This is the invariable rule in mining shafts, and preventive measures must always be devised and used, by means generally of air apparatus, to temper the heat as the depth is augmented, else deep mining would have to be abandoned. The rate of increase has been variously estimated by different scientists in widely distant portions of the globe. A few of them may be mentioned at this place, since it was upon a total miscalculation on this head that led to the present most deplorable results. The editor of the _Journal of Science_, in April, 1832, calculated from results obtained in six of the deepest coal mines in Durham and Northumberland, the mean rate of increase at one degree of Fahrenheit for a descent of forty-four English feet. In this instance it is noticeable that the bulb of the thermometer was introduced into cavities purposely cut into the solid rock, at depths varying from two hundred to nine hundred feet. The Dolcoath mine in Cornwall, as examined by Mr. Fox, at the depth of thirteen hundred and eighty feet, gave on average result of four degrees for every seventy-five feet.