374 ARRAN. GEOLOGY. SECONDARY STRATA. 



near the ruined Salt pans. They are thin, and divided, 

 like some septaria, into polygonal plates, which are how- 

 ever separated by mere fissures, without any interme- 

 diate substance. The divisions of one of the beds are 

 rectangular, so that the surface resembles a sort of pave- 

 ment in parallelograms; those of another are hexagonal, 

 or variously polygonal ; both of them presenting the arti- 

 ficial aspect of a brick pavement. In one of these cases 

 the divisions are strongly marked by a sort of concave 

 moulding, parallel and close to the edge of each piece, 

 so as to add much to the artificial appearance of the 

 whole. This substance is here rare, since it only occurs 

 in the place now described, while there are many alterna- 

 tions of the other strata above mentioned. 



Nearly in the same place, the coal which was formerly 

 wrought in this island is to be observed. It is said to have 

 occupied three distinct beds, but the ground is at present 

 in such a state that it is not possible to trace them. From 

 the actual appearance of the old workings, which are how- 

 ever exceedingly obscured by water and rubbish, I should 

 rather judge that all the pits had been sunk on the edge 

 of the same bed, which, having a considerable dip, like 

 the rest of the strata in this place, is here turned upwards. 

 Although the bed itself cannot be examined, its position 

 may be deduced from the examination of the surrounding 

 parts, while its nature may be conjectured from the mate- 

 rials which are scattered about in the vicinity. It ap- 

 pears to repose immediately on the red sandstone, and to 

 be followed by a thick series of white calcareous sand- 

 stone ; these being again succeeded, although at a consi- 

 derable distance, by a repetition of the red sandstone. The 

 whole are followed very speedily by the schist, that rock being 

 of course subjacent to them; whence we may infer that 

 at the point where it has been wrought, the coal lies 

 at the very edge of the secondary strata. The substances 

 which immediately accompany it, are black argillaceous 

 sandstone, the same rock of a mixed black and white 



