Page:Quarterly Journal of the Geological Society of London, vol. 28.djvu/548

452 mid-terrace gravel below. These strips of London Clay are seen at Hanwell, at Acton, and for upwards of three miles from Kensington to Temple Bar, always at an average level of 50 feet. Along the sides of all the tributary streams, the Brent, the Acton stream, and the Serpentine, this strip of the London Clay is also found at about the same general level of 50 feet, dividing the high- terrace gravel into patches. The lower margin of the mid-terrace gravel runs from the river at Kew, by Chiswick House to Chiswick, where it again joins the river; all below this line, in the bend of the river, is the third, or low-terrace. In the next bend of the river to the eastward, the margin of the mid-terrace is not so well defined; but Mr. Whitaker has traced it along the river below Hammersmith to Fulham Church, and thence to Sandy End and Walham Green, and to the river at Cremorne. South of the river we have low-terrace at Ham, Petersham, Richmond, Kew, East Sheen, Barnes, Putney, Wandsworth, and Battersea. The mid-terrace is wanting, except between Barnes and Putney, to the north of the Barnes stream. A line of high-terrace gravel runs from Richmond Hill to East Sheen, commencing at the height of 50 feet. At Roehampton and Putney Heath, the high-terrace, if it be high-terrace, runs no lower than the 100-feet line, and rises to the height of 170 feet on Putney Heath. On Wandsworth and Clapham Commons the gravel rises to the height of 100 feet; this Clapham and Wandsworth gravel Mr. Prestwich formerly regarded as high-level, and considered it to form the same plain with that of Putney Heath. But both Mr. Prestwich and Mr. Whitaker, I beheve, now consider the Wandsworth and Clapham to be high-terrace gravel, whilst that of Putney Heath and Wimbledon Common may be high-level gravel or a higher terrace of the river-gravel; certainly, if the level is to be taken as the criterion of classification, the Clapham and Wandsworth gravels would appear to correspond with the high-terrace gravel on the north side of the river, and to be somewhat lower than that of Wimbledon Common. As on the north, so on the south side of the river, the high-terrace gravels are divided from the mid- or low-terrace gravels by strips of the London Clay throughout nearly the whole of this district. Above Ham and Petersham the strip rises to a considerable height in Richmond Park. From Richmond to East Sheen, the upper margin of the strip, and the commencement of the high-terrace gravel, judging by Mr. Mylne's map, appears to be on the 50-feet line, whilst the mid-terrace gravel ends in about the 30-feet line. On the Roehampton and Putney-Heath hills the mid-terrace rises to the 50-feet line, while the upper-terrace gravel commences at about 100-feet, leaving the space between the 50- and 100-feet lines occupied by the strip of the London Clay.

It seems to be doubtful whether or not this strip of clay runs along