494 MR. CLEMENT REID ON THE [Aug. 1 896, 



Reading Beds and London Clay near Dorchester were so tilted as to 

 lead to a sharp transgression of the overlying Bagshot gravels. It 

 happens thus that within a distance of 3 miles the Bagshot 

 gravels cut through both those formations. A short distance farther 

 west, at Bincomhe Down, the gravel has cut well into the Chalk, 

 and there is little doubt that within a few miles it must have over- 

 lapped all the Cretaceous rocks and cut into Purheck Beds. The 

 reason why it is suggested that the Purbeck stones can only have 

 come a short distance will be seen on looking at a geological map. 

 Purbeck rocks might be obtained in the immediate neighbourhood 

 of the Bagshot gravels, on the south side of the Bincombe fault ; but 

 they could not have been derived from regions farther west, as in 

 that direction the Purbeck Beds had already been denuded and over- 

 lapped by the Greensand. This overlap becomes more pronounced 

 westward, the Greensand resting unconformably on all the Second- 

 ary rocks, till at Haldon there is nothing between the Greensand and 

 the Permian breccias. It thus comes about that no Jurassic fragments 

 are found in the Bagshot gravels, with the exception of Purbeck 

 rocks, which seem to have bordered the southern edge of the Eocene 

 valley. The rest of the gravel was apparently derived from the 

 higher part of the river-basin, where Greensand rests directly 

 on Permian strata, even the Budleigh Salterton pebble-bed being 

 overlapped and hidden. 



It is noteworthy that the new evidence discovered in the western 

 end of the Hampshire Basin strongly supports the idea that the pipe- 

 clays of the Bagshot Series are derived from the weathering of the 

 Dartmoor Granite, and that the Bovey Tracey outlier, so like the 

 deposits around Bournemouth, is, as maintained by Mr. Starkie 

 Gardner, of the same age and deposited in the same basin, though 

 in Devon Eocene rest directly on Palaeozoic rocks. Bovey Tracey 

 is only a short distance from Haldon, and Permian breccias, Culm 

 Measures, and granite rise into hills in the immediate neighbour- 

 hood. That district might have provided the whole of the material 

 in the Bagshot gravels, with the exception of the Purbeck marble. 



A consideration of the evidence now brought forward shows that 

 besides the already-recognized earth-movements of intra-Cretaceous, 

 early Eocene, Miocene, and Pliocene dates, there must have been 

 folding during at least one other period in the same or closely ad- 

 joining areas. The earliest, or intra-Cretaceous, folding accounts 

 for the marked unconformity of the Upper Cretaceous on all the 

 older rocks. The second disturbance, either late Cretaceous or 

 early Eocene, during which the Bincombe overthrust must have 

 commenced, caused Beading Beds to overlap the Chalk and rest on 

 Upper Greensand. A third disturbance allowed Bagshot Beds to 

 cut across the upturned edges of the London Clay. Beading Beds, 

 Chalk, and Greensand and reach the Purbeck and older rocks. 

 Einally we have the well-known Miocene folding, which threw the 

 whole of the Tertiaries of the Hampshire Basin into a series of 

 sharp undulations with an east-and-west axis, and this movement 



