192 MR. H. W. MONCXTON ON SOME GEAVELS [May 1898, 



' Eiver- and Valley-Deposits,' whereas the Fox Hills plateau is 

 mapped as ' Hill-gravel and Sand of doubtful age and origin.' I 

 believe that both are river-gravels of about the same age, and I do 

 not quite appreciate the reason v^'hich has led to different colours 

 being used for them on the Geological Survey map. 



The gravel of the plateau at Farnham is in places 25 feet or more 

 thick. As a rule, there is little or no sign of stratification, the 

 gravel consisting of a mass of stones closely packed together, but in 

 places where the gravel is sandy it is seen to be well stratified. I 

 took a photograph of a part of one pit, where the stratification was 

 particularly well shown on a north-and-south face, about | mile 

 south-west of St. Thomas's Church.^ 



The gravel consists mainly of flint. Flint-pebbles occur, also 

 pebbles of ironstone, some Lower Greensand chert, and a little 

 quartz. The gravel rests partly on Folkestone Beds and partly on 

 Gault, and the Chalk-flints may have come from the north, west, or 

 south-west, probably from older gravels or Clay-with-flints. The 

 cherty fragments doubtless came from the Hythe Beds, which now 

 crop out some 4 miles south of the plateau. 



On the south-eastern side of the plateau there is a small valley, 

 and on the opposite side patches of gravel occur at about the same 

 level, which are mapped ' Hill-gravel,' etc. I have, however, 

 no doubt that they are river-gravels practically contemporaneous 

 with the Farnham gravel ; it is interesting to note that the pro- 

 portion of chert is larger, and that there are few or no flint- 

 pebbles from the Tertiary pebble-beds (I saw only poor sections, so 

 cannot speak with certainty as to the proportions), which is what 

 one would expect from their situation. 



There are two terraces of gravel on the north-west of the Farn- 

 ham plateau, one at a level of about 300 feet above Ordnance 

 datum, and the other about 250 feet. The upper terrace, 12 feet 

 or more thick in places, consists mainly of brown subangular flints, 

 and the sections that I have seen do not show much sign of strati- 

 fication. This may be of the same age as the gravel at Ash, in 

 which there is a large pit 285 feet above Ordnance datum. It 

 shows a good section of 6 feet of yellow and reddish gravel, much 

 contorted, though with little other sign of stratification. But this 

 was only a local feature, for in the large pit north of the road and 

 at the same level the gravel is well stratified. This terrace is 

 probably connected with the river which deposited the gravels at 

 Great Bottom Flash, Mitchet Lake, etc. It seems to me clear 

 that these extensive terraces on the side of the Fox Hills must 

 owe their origin to a river with a drainage-area extending much 

 farther south than that of the modern Blackwater, and I therefore 

 suggest that the terraces of Farnham owe their origin to the same 

 river. 



This flat, or slightly sloping, expanse of gravel of Mitchet Lake 

 bears a curious resemblance to the gravel-flats at the top of the 



• ^ The photograph is no. 1324-of the Brit. Assoc. Committee Geol, Photogrs. 



