Page:Quarterly Journal of the Geological Society of London, Volume 24.djvu/236

118 118 PEOCEEIXTNGS OF THE GEOLOGICAL SOCIETY.

are none characteristic of any particular elevation above the river. Bones and flint implements are said to be found throughout the Amiens gravels ; but as I have never found any myself, nor seen any found, I cannot speak on this point from observation ; and it does not appear that these remains, any more than the shells, Tvould enable us to distinguish any particular level.

The large stones of Gres are abundant in all the quarries. I made notes of the numbers and sizes of all I observed, and found that they are also distributed as much in the gravel above the railway as below it, and range up to 4 feet long. There are as many and as large blocks of Gres in the Moutiers northern pits as in those at St. Acheul. I observed one Gres at La ISTeuville partly covered by loess, the rest of the stone being on gravel ; but elsewhere the Gres stones were always in the gravel.

I have mentiolied the loess being a very good brick-earth at a point 120 feet above the sea in Montiers. The colour and material of the loess is generally a dull brown, varying in proportions of clay and sand and in the amount of angular flints contained in it through- out the whole area. 1 have, however, remarked a reddish friable brick-earth on the terraces fringing the Somme at Longueau, ninet}^ feet above the sea. This is probably of the same character as that in the similar terrace at jSTeuviUe and Montiers. This brick-earth is very similar to that of the Eiver Lea ; indeed at Clapton there is a well-marked terrace of brick-earth bounding the marshes, which are composed of gravel. The Clapton terrace is higher than that of the Somme at Amiens, and reposes on London clay, instead of chalk as at Amiens.

This low escarpment of loess is to be seen for a great many miles eastward along the Somme ; and, from the angle at which it faces the river, with its flat top, it so resembles a military earthwork that it is often regarded as artificial. I have measured the escarpment at five or six points ; and the angles vary from 20° to 40°, the average being 35° (figs. 9 and 10.)

In the Saveuse valley the angles are also various. I have often remarked similar escarpments in England. I made a note of a

Pig. 9. — Section near Cagny, in the valley of the Arve. Loess Terrace just above the level of Marsh.

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series of terraces, seven in number, one over the other, on the chalk hills, on the north side of the Somme valley, about nine miles from Amiens, on the Paris line ; and, indeed, in the space of ten miles you may see twenty small lateral valleys opening into the