Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/124

86 S. Y. WOOD, JTTN., AND F. W. HARMER ON THE 23rd vol. of the Journal, because, although the succession of all the beds out of which the valley is cut are correctly represented in them the sweeping-down of the Middle Glacial over the edges of the Lower Glacial and Crag, such as is shown in section V. of the present paper, is not introduced, we not having then discovered it. The figure (no. 1) given in the 23rd vol. (p. 88) of the bed at Trowse shows that the clay there is partially overlain by brickearth and sand, much in the same way that the bed in the Blackwater valley (section XXIII. of the present paper, p. Ill) is overlain. The sand over the brick-earth at Trowse, and the gravel over the brick-earth at Appleford bridge in the Blackwater valley, seem in both instances to show the transition upwards of this interglacial valley-bed into the Middle Glacial. The Middle Glacial sand overlain by the Upper Glacial of the pit at Tuck's- Wood farm on the hill above the Trowse section indicates, we now think, part of the infilling of the Yare valley which had been denuded interglacially out of the Lower Glacial and Crag beds and the Chalk ; and fig. 6 represents what we think the relative position of the several beds is most likely to be. Fig. 6. — Section VI., at TucVs-Woocl Farm. (Length 2 miles. Vertical scale 17| times the horizontal.) N. Cutting at Pit at Pit at S. Victoria Tuck's-Wood Trowse River Station. Farm. Junction. Yare. A /4 r 1, V, 4, 5, 6, 7, and 8 as in fig. 5. a. Bed of clay chiefly made up of chalk debris and partly overlain by thin Brick-earth and by sand. 10. Postglacial valley-gravel and recent alluvium. The dotted line indicates the supposed continuation of the interglacial valley beneath the recent alluvium. Pursuing now the valley of the Wensum, the following three small lines of section (Nos. VII., VIII., and IX.) are necessary to illustrate its interglacial excavation, as we are not able to give a line across both sides of the valley at any one point which can be sufficiently verified by open excavations, abundant even as these are over the country traversed by this valley. The lines of these sections are taken at distances (following the sinuosities of the valley) of 20, 29, and 39 miles respectively above Norwich, section VII. being the lowest, and IX. the highest up the valley. It often happens towards the upper end of the valley that the Upper Glacial rests direct on the Contorted Drift ; and some good sec- tions of the two in contact occur near Guist in the Wensum valley ;