Page:Popular Science Monthly Volume 12.djvu/83

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MAN AND THE GLACIAL PERIOD.

is not only possible, but more probable. That other interpretation I have indicated in the general section (Fig. 5), in which all the facts observed are incorporated. I consider that the dark clay with vegetable remains and bones of the large extinct mammals is preglacial, in the sense that it is older than any of the glacial beds of the district. The gravel below the "redbrick earth," in which Mr. Frere found the flint implements, is probably of the same age, or that of the overlying gravel (5 in Figs. 4 and 5). That the implements, and also fragments of bones and wood, should be occasionally found in the overlying deposits, is what might be expected, as they were in great measure formed by the denudation of the older ones. The "red-brick earth" (4 in section) is, I believe, a true glacial clay, belonging to the latter part of the first European lake. It is a noticeable fact that, all over Northern Europe, the glacial clays burn to a red color—a point not without significance with regard to the red beds of Permian

PSM V12 D083 Soil layers of glacial activity.jpg
Fig. 9.—1. Sandy "trail" with flints—three feet. 3. False-bedded sand and subangular gravel—four feet six inches. 4. "Red-brick earth," yellow and unstratified at top, graduating downward into gray, laminated, calcareous clay; shells of Bithinia tentaculata and Limnea palustris abundant at its base, where there is about six inches of sandy clay—four feet six inches. 6. Clay similar at top to the lower part of the "red-brick earth," but with more chalk-grains, gradually more chalky downward, and with stones like the upper portion of the lower bowlder-clay at point A in general section.

or Triassic age. The false-bedded sands and gravels (3 in Figs. 4 and 5) belong, I think, to the middle glacial series, and the clay (2 in Figs. 4 and 5) is, I think, the upper bowlder-clay. These views are only theoretical, but I claim that they are based upon as sound a foundation, and are as much in accordance with the facts of the case, as those generally received.

Another interpretation is tenable, namely, that the lower bowlder-clay underlies the brick-clays, and that the upper bowlder-clay overlies them, while they themselves belong to a warm interglacial period, as held by Messrs. Croll and Geikie. I do not agree with this opinion, as I can nowhere find any evidence of a warm interglacial period, and am unwilling: to believe that there were more post-tertiary glacial periods than one, when one will explain all the phenomena; but if it were to turn out that the lower bowlder-clay does exist beneath the brick-clays at Hoxne, it would be one of the strongest facts in its favor yet brought forward.