at the equator; and the great lands and great oceans of our planet, instead of running, as they do, in so remarkable a manner, from south to north, would range, like the belts of Jupiter, from west to east. There is no escape for us from the inevitable conclusion that our globe received its form, as an oblate spheroid, at a time when it existed throughout as a viscid mass.' Accordingly, though admitting that 'there is a wide segment of truth embodied in the views of the metamorphists,' Miller declared his belief on the subject of central heat in these terms: 'I must continue to hold, with Humboldt and with Hutton, with Playfair and with Hall, that this solid earth was at one time, from the centre to the circumference, a mass of molten matter.' Hugh Miller saw the ninth edition of Sir Charles Lyell's 'Principles,' and seems to have had its reasonings in view in writing these and other passages; we cannot persuade ourselves that he would have recalled them if he had lived to see the tenth edition. We wish to state in the clearest terms that, though we have stated some of the evidence which supports the ordinary geological doctrine of central heat, we do not adduce that evidence as absolutely conclusive. All we argue for is, that the question be not looked upon as decided in favour of the uniformitarians. It may be that more minute and comprehensive observation on the age of the crystalline rocks and on the phenomena of metamorphism will demonstrate that the condition of no system of rocks known to us can be traced to the influence of an originally molten state of the planet. It may be that what seems at present the unanimous opinion of astronomers, that 'the whole quantity of Plutonic energy must have been greater in past times than the present,' is a mistake; it may be, in the last place, that the primeval fusion of the planet ceased to act upon those parts of the crust which are accessible to geological observation before those causes came into operation to which their present state is due. But we deny that these positions are established. A writer in the _Edinburgh Review_ declared, so recently as last year, that M. Durocher, in his 'Essay on Comparative Petrology,' has produced 'absolute proof that the earth was an incandescent molten sphere, before atmospheric and aqueous agencies had clothed it with the strata so familiar to our eyes.' Sir Roderick Murchison, who, as a student not only of books and museums, but of the rock-systems of the world in their own vast solitudes, is an authority as high as any living man, holds that 'the crust and outline of the earth are full of evidences that many of the ruptures and overflows of the strata, as well as great denudations, could not even in millions of years have been produced by agencies like those of our own time.' These statements may be correct or the reverse; but they prove, we submit, that the controversy respecting central heat is not at an end.