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Geological |iotes on ®x1>ov Hoto, 



By H. H. Arnold-Bemrose, M.A., F.G.S. 



HE monoliths, or slabs, are composed of a white- 

 coloured variety of mountain limestone, which con- 

 tains few fossils and slight traces of iron oxide. 

 The faces of the slabs are parallel to the bedding 

 planes of the rock. The edges, which in some cases are very 

 true, are defined by the joint planes. 



There is no doubt that these slabs were at one time placed 

 vertically, with one end in the ground and arranged in pairs 

 in a rough ellipse. Embedded in the ground and projecting 

 above the surface are the stumps of several slabs, shewing 

 where the latter have been broken off. In some of these stumps 

 the bedding planes are evidently vertical.* 



Such slabs might have been found almost ready to hand 

 within the neighbourhood. The mountain limestone is 

 traversed by divisional planes called joints. They often run 

 in sets at right angles to each other, and to the bedding planes. 

 The mass of limestone is thus divided naturally into a number 

 of slabs or blocks, the size and shape of which vary with the 

 thickness of the beds, and the distances between the joints. 

 In quarrying, advantage is taken of these joints. The upper 

 surfaces of some of the slabs on Arbor Low are very irregular, 



* In his address to the Society — given at Arbor Low on June 29th, 1901 

 — Mr. H. A. Hubbersty, whilst endorsing the vertical theory of these slabs, 

 suggested the probability that they were purposely thrown down at the 

 Roman conquest of Britain. — En. 



