¹ I observe that Colonel Greenwood, in your last number (p. 395), ridicules the phrase “meteoric,” as applied to the sub-aërial denuding agencies, instead of “rain and rivers.” But can he not see that his favourite formula leaves out the influences of alternate frost and thaw, of snow and ice, of electricity, chemical decomposition, etc., all more or less effective in wearing away the exposed surfaces of land? The Colonel seems, too, to claim for himself the origination of what he calls “the rain and river theory of erosion.” Now, without denying the “originality” of much in Colonel Greenwood's volume, yet its first edition was printed only in 1857, and geologists are well aware that through half a century before that date the doctrine of the enormous influence of atmospheric agencies (rain and rivers inclusive) in moulding the surface of the earth had been earnestly advanced by Hutton, Playfair, Lyell, myself, and others. (See Quarterly Review for June, 1827, p. 477.)