492 ME. CLEMENT EEID ON THE [Aug. 1 896, 



undergone by the Reading Beds, but far more marked. The 

 Bagshot Sands become coarser and gravelly, unworn flints and 

 flint-splinters become abundant, and mixed with these is found a 

 quantity of subangular Greensand chert, like that occurring in the 

 Beading Beds. There is, however, one character which enables us 

 easily to distinguish between the Bagshot and Reading gravels. 

 The Reading gravels consist of flint and chert, with an occasional 

 quartz-pebble : careful seareh yielding nothing else except one or 

 two small quartzite and grit-pebbles. Bagshot gravels, on the other 

 hand, contain, besides flint and chert, so much quartz and hard 

 subangular Palaeozoic rocks as to make the finer screened material 

 look like a Cornish beach. They yield also a certain quantity of 

 Purbeck marble and other Purbeck rocks, though I have been unable 

 to discover any trace of Portland Beds or of the Oolites below. 1 



This gravelly condition of the Bagshot Series first becomes 

 conspicuous in the large pits close to Moreton railway-station, where 

 40 feet or so of the sands can be seen associated with seams of white 

 pipe-clay. In this pit one can find fragments of all the rocks which 

 occur in the coarser gravels farther west. It is noticeable also 

 that the chert-fragments found in the lower part of the pit are 

 often quite soft, so that they were at first mistaken for pebbles of 

 pipe-clay, though they soon harden on exposure to the air. A 

 softening of the chert-pebbles will explain the curious way in which 

 the fragments are sometimes dented by each other and pitted by 

 sand-grains, at a locality where neither earth-movement nor 

 pressure has ever been extreme. As I found rounded quartz-grains 

 half embedded in some of the flints it is possible that Chalk- flints 

 also can to some extent be softened in a similar way. 



To the west of Moreton the Bagshot gravels rapidly become much 

 coarser, and as they change the Bagshot Series cuts through the 

 London Clay and through the Reading Beds, till it rests immediately 

 on the Chalk. The various outliers south and south-west of Dor- 

 chester all belong to the Bagshot Series, not to the Reading Beds as 

 formerly supposed. 



A study of the composition of the Eocene gravels shows distinctly 

 that the rivers that brought them must have flowed from the west 

 or south-west. Both Reading and Bagshot gravels become coarser 

 and the stones more angular in that direction, and seem to occupy a 

 valley eroded in the Secondary strata. But of the extent of this 

 erosion it is difficult to obtain direct evidence, for the wide trough 

 south-west of Dorchester, in which several of the Eocene outliers lie, 

 is mainly a continuation of the syncline of the Hampshire Basin, 

 not an eroded hollow. A considerable amount of erosion of the 

 Chalk seems to have taken place before the Ridgeway and Black- 

 down (Hardy's Monument) outliers were deposited ; but I am quite 



1 Some of these rocks are recorded by Sir Joseph Prestwich as occurring at 

 BLackdown in gravel, which ' may belong to some part of the Gk cial period,' 

 overlying the Eocene beds. The gravels seem to me to be of Eocene age. See 

 Quart. Journ. Greol. Soc. vol. xxxi. (1875) p. 41. 



