Until Geology began to take the place of a science, few, if any, troubled themselves about the age of our planet. The habit of thought, created partially by the Mosaic Cosmogony, which led us to look at all the natural features around us as if but just freshly formed by the hands of the Creator was not favourable to any such inquiry.

One of the most important questions which modern geologists have to answer is that which refers to the duration of Geological time. How long is it since the Glacial epoch? What was the date of man's appearance on the earth? How many ages have rolled by since the earth first became the habitation of organized beings? Such are the questions, daily repeated, to which we must make some answer, or, if need be, honestly confess our ignorance.

As I am one of those who find difficulty in understanding the preservation of stratified deposits beneath the Till, I would like to point out to Mr. J. Geikie that he has not correctly stated the difficulty in his paper (Geol. Mag. Feb. 1878) on “The Preservation of Deposits under Till or Boulder-clay.” The difficulty really lies in the explanation of how the Till itself was deposited: were that clear, the preservation of beds beneath it might be at once intelligible. Admitting the passage of an ice-sheet across the country, admitting further that the Till is the moraine profonde of such an ice-sheet, the accumulation of 100 feet of Till beneath the ice-sheet is a phenomenon which has not been explained, and cannot be passed over as unimportant. A moving mass of ice, 2000 feet thick, seems a formidable agent of erosion; yet where I now write nearly 100 feet of Till intervene between the surface and the Carboniferous rocks, which, where exposed, shows striations having the usual compass bearing for this neighbourhood. The greater portion of the Till hereabouts is derived from the Carboniferous rocks of the district, but numerous boulders of granite, felstone, schist, and of Old Red Sandstone sedimentary and volcanic rocks, show that the ice had brought materials from a wider area. The limits of the Carboniferous series are about twelve miles to the west and northwest of Glasgow, that being the direction whence the ice came. As the ice of a modern glacier pushes the results of erosion before it, we may conclude that the old ice-sheet with a pressure of about 1000 lbs. to the square inch did the same; indeed, Mr. Geikie has already accepted this “idea as to how an ice-sheet would behave,” but without explaining how the alternate exposure and concealment was effected in the presence of very thick Till. It may be said that the ice pushed its moraine profimde before it, but then Hugh Miller's “pavements” have always been referred to as proofs that the ice overrode not displaced the Till already accumulated.

In a paper on the Lias of Ilminster, by my friend Mr. Charles Moore, F.G.S., communicated to the Somerset Natural History Society, and published in their Proceedings (1865–6, vol. xiii. p. 72), I gave a list of the Crustacea submitted to me for examination by Mr. Moore, among which was a species belonging to the genus Penæus, referred by me to P. latipes, Oppel, from the Upper and Middle Lias of Ilminster.