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field near the southern edge of which tlie members were tlien 

 standing. Triangular in shape, its apex was at Toilworth, its base 

 the range of the Meudips, its eastern boundary ranged through Wick- 

 war to MeUs, its western was the three groups of limestone hills — 

 Knole Park and the Ridgway ; Leigh Down ; and Broadfield Down 

 — the latter was the last and most southern limestone anticlinal 

 ■which divided the several basins. Having explained the position 

 of the beds dipping away from the centre on each side at an angle 

 varying from 5° to 25°, he said that, like the Mendips, its trend 

 was in an easterly and westerly direction. Its saddle-back shape 

 was probably due to the form of the Old-red-sandstone beds below, 

 which, though unexposed on the Down, formed the core of and 

 were visible on the Mendips, and likewise were seen at the base of 

 the rocks in the Avon gorge. The peculiar cavernous features of 

 all hmestone districts were then touched upon, and the common 

 occurrence of ravines generally at right angles to the trend of the 

 hills. Then came the question how these ravines were formed ? 

 and the members were left to their own conclusions whether that of 

 Brockley, which they had just ascended, or that of Goblin, at the 

 head of which they then were assembled, was due either to the 

 erosion theoiy of water cutting its way gradually down from above, 

 assisted by the effects of frost and heat ; or of water acting 

 chemically and mechanically in the interior of the rocks, forming 

 passages and caverns, the roofs of which being gradually eaten away 

 step by step in the course of countless ages, finally assumed the 

 form of ravines (this theory the membei-s might remember was 

 ably placed before them by one of their honorary members, Mr. 

 Boyd Dawkins, during one of their past excursions) ; or to the 

 dislocation theory, which called in earthquakes and igneous agency 

 to its assistance. There was yet another theory, which, as it 

 combined the other tv^o, might be worthy of consideration ; that 

 was the one which attributed these gorges to disturbances in the 

 crust of the earth, causing lines of weakness in various directions 

 which the water sought out and enlarged into ravines and gorges. 

 Sufficient theories, however, were placed before them to create any 

 amount of discussion. The evidence on all sides of gi-eat denuda- 

 tion was then pointed out ; e.g., the Dolomitic conglomerate which 

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