JF, II. Hicdieston — Creechbarro/v hi Piwheck. 245 



represented in the geological map as passing along the junction 

 of the Chalk and Tertiaries about 300 yards to the south of our 

 present position [i.e. on Creechbarrow]. It is quite possible that, 

 instead of sticking to that route, the line was deflected somewhat, so 

 that the thrust-plane has come in among the Tertiary clays. . . . 

 The great thrust from the north has pressed these clays against the 

 hard Chalk, making them harder and fitter to withstand the forces 

 of denudation." ' Remarkable instances of derangement of the 

 strata and reversal of dip have been experienced in the pipeclay 

 workings, and the Chalk itself is found to be dipping to the north 

 at an angle of 80° at the limekiln which is close to Creechbarrow. 

 In consequence of such evidence of the effects of the Isle of Piirbeck 

 thrust-fault in this immediate district, it occurred to me at that 

 time that exceptional tectonic forces, locally exerted, might possibly 

 have had something to do with the formation of this peculiar hill. 

 So much for theory No. 2. 



(3) The third explanation olfered was the most theoretical of 

 all, as it involved a spread of Plateau-gravel on the summit of 

 Creechbarrow at some period of its history. Everyone knows 

 how largely the Plateau-gravel has contributed to the formation 

 of high ground, more especially in the Bagshot districts of Surrey, 

 Hants, and Dorset, so that what was originally a shallow valley, 

 owing to the protection afforded by an accumulation of flint gravel, 

 often cemented by iron-oxide, becomes relatively high ground and 

 sometimes even a hill.^ On this occasion I went so far as to 

 express my belief that there had been Plateau-gravel on the top 

 of Creechbarrow. The principal evidence for this hypothetical bed 

 of gi-avel arises from the fact that about a thousand yards from the 

 summit of the hill on the north side, near the 300 feet contour, there 

 is a large deposit of clayey gravel, which is worked for road-metal 

 and probably for other purposes. This bed of gravel, it then 

 appeared to me, might be the remains of a deposit once at a much 

 higher elevation, which had, to a certain extent, been slid off these 

 slippery clays, especially during a period when there was a great 

 deal of snow, which would facilitate deposit on the north side of 

 a slope. Another indication of this supposed gravel bed on Creech- 

 barrow, which was then present to my mind, arises from the great 

 number of peculiarly large flints which may be seen about the hill. 

 They are, for the most part, unabraded flints, and their position is 

 such as to suggest that many of them may have rolled down from 

 the upper part of the hill, though they are now to be noticed 

 principally on the eastern base. These loose flints I held as 

 additional evidence of the existence of my hypothetical gravel bed 

 on the top of this hill. So much for theory No, 3. 



^ Op. et vol. cit., p. Iviii. 



- The valley-flat of days gone by 



Becomes the plateau, high and dry : 

 Thus, in the cycle of the Ages 



The Drifts reverse their earlier stages. 



Anox. 



