Page:Popular Science Monthly Volume 12.djvu/77

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67
MAN AND THE GLACIAL PERIOD.

most every section, from Norfolk into Surrey. It is everywhere seen in the Thames Valley lying on the top of the lowland gravels, and is shown in great perfection in the long section now (March, 1876) exposed between Acton and Hanwell, on the Great Western Railway.

PSM V12 D077 Soil layer composition 1.jpg
Fig. 1.—Scale twelve feet to one inch. 1. Sandy clay, or "trail." with patches of sand (S) and scattered flints, mostly in nests, at the irregular base of the deposit. 3. Sands and gravel, false-bedded with lenticular beds of sand (S), and in the lowest seams rounded pebbles of chalk.

It generally, if not always, rests upon an irregular surface of the beds below it, and contains stones derived from some other source.

On the south side of the Waveney, at Syleham, there are good sections on both sides of the turnpike, and these exhibit similar false-bedded sands and gravels, which are, however, covered by the upper bowlder-clay instead of by "trail." Fig. 2 shows a section exposed

PSM V12 D077 Soil layer composition 2.jpg
Fig. 2.—Brown bowlder-clay. with many whole flints, and with angular patches of red sand (B) marly clay with small stones (A), and red bowlder-clay (C). 3. Sands and subangular flint, gravel with rounded pebble of quartz, and (in the lowest seams) of chalk.

on the south side of the turnpike. A little farther west, on the north side of the turnpike, is another gravel-pit, showing a similar succession, but with the beds of sand and gravel strongly false-bedded. In all these sections small pebbles of chalk are very abundant in the lowest beds. The most remarkable feature in the upper bowlder-clay is the numerous angular patches of material quite different from the matrix of brown clay. The angular patches of red sand are very peculiar and difficult to explain.

In a large gravel-pit a little north of Oakley Church there is a long