In other planets, he urged, the same form is due manifestly to the action of the same law. Venus, Mars, Saturn, oblate spheroids all, have been similarly 'spun out by their rotatory motion in exactly the line in which, as in the earth, that motion is greatest.' In these, however, we can only approximately determine the lengths of the equatorial and polar diameters; 'in one great planet, Jupiter, we can ascertain them scarce less exactly than our own earth;' and Jupiter's equatorial diameter bears exactly that proportion to his polar diameter which 'the integrity of the law,' as exemplified in the relation between the equatorial and polar diameters of the earth demands. 'Here, then,' proceeds Miller, 'is demonstration that the oblate sphericity of the earth is a consequence of the earth's diurnal motion on its axis; nor is it possible that it could have received this form when in a solid state.'
Sir Charles Lyell holds that the excess of the equatorial diameter over the polar may be accounted for on uniformitarian principles. 'The statical figure,' he says, 'of the terrestrial spheroid (of which the longest diameter exceeds the shortest by about twenty-five miles), may have been the result of gradual and even of existing causes, and not of a primitive, universal, and simultaneous fluidity.' Miller denies this possibility; and we confess that the passage in which he assails the position of Sir Charles Lyell appears to us to have great force. Let us hear him:--
'The laws of deposition are few, simple, and well known. The denuding and transporting agencies are floods, tides, waves, icebergs. The sea has its currents, the land its rivers; but while some of these flow from the poles towards the equator, others flow from the equator towards the poles uninfluenced by the rotatory motion; and the vast depth and extent of the equatorial seas show that the ratio of deposition is not greater in them than in the seas of the temperate regions. We have, indeed, in the Arctic and Antarctic currents, and the icebergs which they bear, agents of denudation and transport permanent in the present state of things, which bring detrital matter from the higher towards the lower latitudes; but they stop far short of the tropics; they have no connection with the rotatory motion; and their influence on the form of the earth must be infinitely slight; nay, even were the case otherwise, instead of tending to the formation of an equatorial ring, they would lead to the production of two rings widely distant from the equator. And, judging from what appears, we must hold that the laws of Plutonic intrusion or upheaval, though more obscure than those of deposition, operate quite as independently of the earth's rotatory motion. Were the case otherwise, the mountain systems of the world, and all the great continents, would be clustered 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.'