of the Great Oolite of Minchinhampton. 117 



clay, we find an alternating series of limestones and clays or 

 marls, extremely variable both in thickness and extent. Certain 

 of these bands, and more especially one of a compact cream- 

 coloured limestone, are eminently shelly, but will seldom allow 

 of the shells being separated entire. These gradually pass down- 

 wards into the middle subdivision, where the rock is more bar- 

 ren of organic remains, and sandy. 



The lower subdivision assumes a very different aspect : we 

 here find 35 or 40 feet of shelly beds, separating into large 

 masses, and well suited for the mason. From the third or lower 

 subdivision it is that nearly the whole of our fossils are derived, 

 the stone usually admitting their being cleaved with a knife. 



The uppermost portion of this series, the planking*, which is 

 from 8 to 10 feet thick, contains the most numerous suite of zoo- 

 phagous Trachelipods, several of which are not found beneath it. 

 To this succeeds a few feet of incoherent sandy rock, the upper 

 part of which is nearly destitute of shells, or only occupied by a few 

 species of small bivalves. The shells gradually increase in number 

 downwards, and repose on several beds of hard shelly rock, 

 locally called Weather stone. Here more especially abound the 

 valves of small oysters, which at length constitute no inconsider- 

 able portion of the mass, and whose peculiar structure imparts 

 such great hardness to the deposit, that the lower few inches 

 strike fire with the tools of the workmen. 



These shelly beds or weatherstones have a high character for 

 durability ; they have a coarse aspect ; when once dried by ex- 

 posure to the sun they do not readily absorb water, and conse- 

 quently resist the action of frost ; a careful selection is however 

 necessary to ensure this desideratum. The south transept of 

 Minchinhampton church, five centuries old, is built of this stone, 

 and notwithstanding its very exposed situation, displays all the 

 sharpness and distinctness in its angles and carving which we 

 should expect in a modern edifice. 



The Fuller's earth which underlies these deposits is but par- 

 tially and imperfectly exposed within the district ; it consists of 

 a series of brown and blue marls and clays traversed by three or 

 four bands of a hard argillaceous rock locally called clay rag. 

 Some portions of the clays, and more especially the rag-stones, 

 are made up of the valves of small oysters, chiefly Ostrea acumi- 

 nata ; the organic remains however are far from numerous 

 when counted by number of species ; they are nearly all bivalves, 

 and I have not observed any which are not likewise found in the 

 weatherstones above. The Fuller's earth constitutes the most 

 fertile soil in this part of the county ; when properly drained it 



* A local term indicating a tliin-be:lded stone. 



