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of the disintegrating forces), but each according tothe quality which our physicists denominate thecoefficient of expansion. Then comes on the longlunar day, at first dissipating the intense cold, thengradually raising the substance of the lunar crust toa higher and higher degree of heat, until (if the in-ferences of our most skilful physicists, and the evidenceobtained from our most powerful means of experimentcan be trusted) the surface of the moon burns (onemay almost say) with a heat of some 500° F. Underthis tremendous heat all the substances which hadshrunk to their least dimensions must expand accord-ing to their various degrees; not greatly, indeed, sofar as any small quantity of matter is affected, but toan important amount when large areas of the moon’ssurface are considered. Remembering the effectswhich take place on our earth, in the mere changefrom the frost of winter to the moderate warmth ofearly spring, it is difficult to conceive that suchremarkable contraction and expansion can take placein a surface presumably less coherent than the re-latively moist and plastic substances comprising theterrestrial crust, without gradually effecting thedemolition of the steeper lunar elevations. When weconsider, further, that these processes are repeatednot year by year, but month by month, and that allthe circumstances attending them are calculated torender them most effective because so slow, steadfast,and uniform in their progression, it certainly does notseem wonderful that our telescopists should from time