Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/356

 colour, apparently derived from chlorite, with purplish stains and including small spherical masses of a white earthy texture, which give to the mass an amiygdaloidal structure: it may be considered as a variety of argillaceous slate, and as it occurs in strata conformable with the usual varieties of the grauwacke formation, it belongs I have no doubt to the same class: it is found to be very useful as a fire stone. The other place where I found a slate very similar to this was in the neighbourhood of Cheddon Fitz-Paine.

§ 10. In passing through the village just named, I observed in the street a small block of stone differing in appearance from any I had found previously, and upon examination I found it to be granite, a rock I had searched for before without success, and indeed this is the only place where I saw an unstratified rock in the whole district, the porphyry and greenstone which accompany the grauwacke formation in Devonshire being wholly wanting here. On inquiry I found that this granite, called by the country people Pottle Stone, came from an old quarry not far distant in the grounds of Hestercombe, belonging to T. Warre, Esq. My informer brought out of his house a whetstone which he said came from another quarry close by the Pottle Stone. It was a greenish compact stone, very like some hornstones or some of those close-grained siliceo-argillaceous compounds which it is very difficult to name. On going to the quarry, which is almost entirely over-grown with brushwood, I found the granite in situ: it is small grained, and consists of dull flesh-coloured felspar, with green mica, and a small quantity of quartz. It occurs in the lower part of the hill and occupies very limited extent. Immediately adjoining is the spot where the whetstones are got. Here I found I regular strata of slate similar to that occurring in many parts of