THAT the skin of our mother Earth's face is wrinkled and shrivelled, is one of the common facts of geology. True it is that with fine feminine instinct she strives to hide the ravages of time beneath a fair covering of grass, moss, and herbage, and gracefully does her best to make her old age comely; and we love her for her skill in covering up the signs of her years. But we are fain, directly we look below the surface, to admit that the wrinkles are there. And the parallel is not a fanciful one, for it has long been a favourite theory among geologists that the wrinkled skin of old age, and the foldings and bendings which are everywhere to be discerned in the layers of the skin of the earth, are due to similar causes. In both cases, something underneath the skin, which in youth kept it stretched and tense, has shrunk away, and the skin has shrivelled up. In the case of the earth it is the gradual contraction of the interior as it cools, which has caused it to draw away from the outer shell; and the crust, as it follows down the shrinking nucleus, has to pack itself into a smaller space, and consequently becomes crumpled up. This explanation is known as the “Contraction Hypothesis.” Numbering as it does many supporters, it has had at the same time some vigorous opponents. In his “Physics of the Earth's Crust,” the Rev. Osmond Fisher was led to the conclusion that the contraction hypothesis would not furnish anything like the amount of elevation that has actually occurred in the case of the earth. We admire the ingenuity and elegance of Mr. Fisher's mathematical work, but we cannot help recollecting Prof. Huxley's warning, that mathematics is like a mill, and that what you get out of it depends entirely on what you put in. Mr. Fisher puts in a supposition made by Sir W. Thomson, as to the way in which the earth cooled. There have been people bold enough to think that in making this supposition a great master of physics for once lent his name to an hypothesis which is in itself physically not very probable; and these same people are inclined to hold that probably Mr. Fisher's calculations tend to show that this is the case, rather than that the contraction hypothesis is inadequate. The Origin of Mountain Ranges considered Experimentally, Structurally, Dynamically, and in Relation to their Geological History. By T. M. Reade (London: Taylor and Francis, 1886.)