Page:Popular Science Monthly Volume 12.djvu/82

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THE POPULAR SCIENCE MONTHLY.

the point marked B in general section—to a depth of seventeen feet from the top of the surface-soil, and obtained the section shown in Fig. 9. The most noticeable feature in this section is the thickening out of the false-bedded sands and gravels, their resemblance to the middle glacial series, and the absence of the "white-brick earth" (7 in section). In a pit a little east of this, Prof. Prestwich and Mr. John Evans found a flint implement in the gravel-bed (3 in section).

PSM V12 D082 Soil layers of glacial activity.jpg
Fig. 8.—1. Sandy "trail" with flints graduating downward into sand, filling pipes in clay below. 2. Unstratified yellow clay, containing isolated angular patches of reddish sand. 3. Whitish sand with a few scattered pebbles, sometimes changing into reddish sand, like that of the patches in the clay above. 4. Yellowish-brown clay ("red-brick earth"), unstratified at top and graduating downward into laminated calcareous clay.

I have now given all the facts at present known respecting the relation of these beds to the Glacial period, and I proceed to the consideration of Prof. Prestwich's theoretical views, as shown in the general section (Fig. 3). In the first place, Prof. Prestwich identifies the bowlder-clay seen in the pit on the east side of the brook as the upper bowlder-clay. As I have already mentioned, it in no respect resembles the clay seen in other sections above the false-bedded sands and gravel, and the existence of the middle glacial beds below this particular deposit is entirely theoretical. Prof. Prestwich makes these sands and gravel to pass under the brick-clays; and I feel confident it will astonish many of those who appeal to this section, as proof of the post-glacial age of palæolithic man, to learn that they have never been seen in this position, and that their presence is an assumption only. The "red-brick earth" ought, according to Prof. Prestwich's views, to thin out eastward, and the dark clays or "red-brick earth" to crop up to the surface from underneath it. Instead of this, as shown in Fig. 8, at the point B in general section, the "red-brick earth" follows down the slope of the hill, and is not underlaid at all at that point by the dark clays. I do not, however, attach much importance to this, as the "red-brick earth" might mantle the hill, overlapping the edge of the dark clays, and yet Prof. Prestwich's general idea of the relation of the latter to the glacial beds be correct. What I do wish to point out is, that that relation is not proved by any of the facts known, and that an entirely different interpretation