Finally, there is a use of the moon which touches us, author and reader, very closely. It has taught us of a world in a condition totally different from our own; of a planet without water, without air, without the essentials to life development, but rather with the conditions for life destruction; a planet left by the Creator—for wise purposes that we cannot fully know—as it were but half-formed, with all the igneous foundations fresh from the cosmical fire, and with its rough-cast surface in its original state, its fire and mould-marks exposed to our view. From these we have essayed to resolve some of the processes of formation, and thus to learn something of the cosmical agencies that are called forth in the purely igneous era of a planet’s history. We trust that we, on our part, have shown that the study of the moon may be a benefit not merely to the astronomer, but to the geologist; for we behold in it a mighty “medal of creation” doubtless formed of the same material and struck with the same die that moulded our earth; but while the dust of countless ages and the action of powerful disintegrating and denuding elements have eroded and obliterated the earthly impression, the superscriptions on the lunar surface have remained with their pristine clearness unsullied, every vestige sharp and bright as when it left the Almighty Maker’s hands. The moon serves no second-rate or insignificant service when it teaches us of the variety of creative design in the worlds of our system, and exalts our estimation of this peopled globe of ours by showing us that all the planetary worlds have _not_ been deemed worthy to become the habitations of intelligent beings.