ON THE BAGSHOX BEDS OF THE LON^DON BASIN. 411 



Lower Bagshot. Ascending the north slope of Eedan Hill, the 

 ground is strewn with angular flints, washed down from the thick 

 capping of gravel above ; but we did not notice any of the rolled 

 pebbles which occur in such profusion on the side of the hill on the 

 opposite side of the valley, as already described. The inference is 

 that there is no pebble-bed here. 



A very fine section is shown in a large sand-pit at the top of this 

 hill east of the railway. In one part of the pit there are 26 feet of 

 white and yellow sands, false-bedded, with thin seams of pipe-clay 

 and irony concretions containing wood. In another part, 10 or 

 12 feet of higher beds of the same character are exposed ; and these 

 are capped by contorted gravels. The beds appear to dip in an 

 easterly direction, but probably in reality rather north of east, as 

 those in Thorn Hill. 



The adjoining railway-cutting through the hill, described by 

 Mr. Irving (Q. J. G. S. vol. xli. p. 501), shows similar sands, with 

 seams of pipe-clay occurring both near the top and about halfway 

 down. We found no marine fossils in the concretions, though we 

 made a careful search both in the cutting and in the sand-pit. 

 Wood, however, is abundant. 



Mr. Irving describes the occurrence of pebbles in a stiff loam in 

 this cutting. We noticed a pebble or two in the sands near its 

 base, but nothing that could be construed into a pebble-bed. Mr. 

 Irving, however, considers the " pebble-bed " here to be the same as 

 that on the south slope of Thorn Hill, and all the yellow sands 

 above it to belong to the Upper Bagshot, and thereupon constructs 

 a diagram (loc. cit. p. 502) giving a southerly dip to the beds in Eedan 

 Hill, though he admits that the beds appear to dip to the east, but 

 draws the inference that the dip is south of east, from the '* occur- 

 rence of a line of pebbles at a level some 15 feet lower in a well- 

 section in the cemetery south-east of the cutting." This cemetery 

 (not that on Thorn Hill) occurs, according to the map, to the North-east 

 of the cutting, which would tend to support our belief that the true 

 dip is rather north of east. iN'ow if Mr. Irving is correct in con- 

 sidering that Thorn Hill and Eedan HiU are similar, he must 

 account for the fact that the sands which he considers Upper, and 

 which overlie his Eedan Hill " pebble-bed," contain pipe-clay seams 

 throughout, and especially well up in the sands. This fact is in 

 itself sufficient, in our opinion, to prove that the sands belong to 

 the Lower and not to the Upper series ; when, added to this, we 

 have the presence of false-bedding, and the absence of all fossil 

 remains except wood, we think there can be no doubt on the point. 

 At first sight, it looks as if the two hills, from their position, 

 must be the same ; but when we consider the ascertained dip at 

 Thorn Hill and the probable dip at Eedan Hill, and their proximity 

 to the sharply tilted beds of the Hog's Back (see the figure p. 376, of 

 vol. iv. of the Survey Memoirs), there is no reason for surprise at the 

 fact that the whole of the beds at Eedan Hill underlie the pebble- 

 bed of Thorn Hill and belong to the Lower Bagshot. Thorn Hill, 

 therefore, we believe to be composed of a base of Lower Bagshot, 



