But astronomy gives a different and more comfortable solution of the problem. The influence of the moon alone, it would appear, acting upon our planet, requires a thickness of crust of at least ONE THOUSAND MILES, to prevent the fabric of the globe from being severed into fragments. The earth, considered in connection with its own planetary system, has three distinct motions in space, a fact in science usually illustrated by the movements of the common spinning-top. A more striking illustration may be seen in the steam-vapor which has aided you onward, that living cloud of light and heat which towers and floats away in these beautifully curling wreaths. Like the trail of the comet, how gracefully it sweeps over the plains in its forward movement: then it turns to the right or left in the direction of the wind: and then, in a third convolution, every globule of the airy mass is twirling on an axis of its own. Equally buoyant is the earth, hung upon nothing, and cleaving the liquid firmament. It turns on its axis, causing the vicissitude of day and night; it moves through its orbit, making the circuit of the sun and the diversity of the seasons; and, in addition, there is an oscillatory motion like the unsteady zig-zag twistings of the carriage-train, occasioned by the excess of the equatorial over the polar diameter. This excess amounts to about a three-hundredth part. But, small as it is, it exerts an assignable influence over the cohesion or attraction of the solid framework. Now, by a nice mathematical demonstration, resting on the sun and moon’s attraction, Mr. Hopkins infers, as indicated by the phenomena of _precession and nutation_, that the minimum thickness of the earth’s crust cannot be less than one-fourth or one-fifth of the earth’s radius. The theorem is of too abstract a nature to be here introduced; but it appears from it that the observed amount of _precession_ requires this degree of solid matter, which gives a clear depth of solid arch over either vacuum, resplendent light, or fiery fluid, of from eight hundred to a thousand miles. This may well allay the fears of the most timid as to the stability of the ground beneath his feet, whatever be the state of the interior, or under whatever modifications the materials therein may exist. II. But if this thickness of crust is required now, it must have been equally required in all past time: hence, it may be argued, no security is thereby afforded against the bursting out of the pent-up fires, or disruption of the outer crust? Now, it has been questioned whether there be such a thing as a CENTRAL fluid heat at all, while the solidity of the earth throughout has been maintained as more in unison with the principles of established science.