110 Dr. FiTTON on the Strata below the Chalk. 



two portions. The upper part immediately succeeding the upper green-sand 

 contains green particles; and thence, for some feet downwards, it is harsh 

 and sandy. The lower portion consists of a smooth, uniform, very plastic 

 clay, of a light bluish grey colour, much in request for the fabrication of tiles 

 and common pottery. It is in this part of the cliff at Copt Point, that the 

 perfect and beautifully iridescent Ammonites, Inocerami, Hamites, and other 

 fossils, have been obtained. From the Point the stratum rises gradually to 

 the west, forming the summit of the hill, about 108 feet in height, on the 

 east of the town of Folkstone ; and some traces of it also exist at the top of 

 the next cliff, on which the church stands. From the coast the gault can be 

 traced in a corresponding situation in the interior, along the foot of the chalk 

 escarpment ; its presence being everywhere indicated by a depression of the 

 surface, and by the marshy aspect of the soil, which generally produces rushes 

 and is strongly contrasted with that both of the chalk above, and of the lower 

 green-sand beneath. 



It is not improbable that in the Isle of Wight and some other situations 

 where the fossils of the gault are rare, the upper and more sandy portion 

 only of this stratum may exist. At Cheriton Tile-works near Folkstone^ the 

 workmen expressly state that it is the lower part only of their pits which 

 affords the shells. 



(12.) Throughout the gault, but chiefly in the inferior portion, concretions 

 of iron pyrites are founds generally approaching to a globular or cylindrical 

 figure, and of a radiated crystalline structure within, or in long thin vermi- 

 cular rods, which at first sight might be taken for vegetable stems. On the 

 opposite coast of France, near Wissant, the pyrites is so abundant in the 

 gault as to have given origin, some years since, to a manufactory of sulphate 

 of iron*; but near Folkstone the quantity is comparatively inconsiderable. 



both from the quantity in which they occur, and their constancy in the colouring matter of 

 green-sand from different locaHties, are sihca, alumina, oxide of iron, magnesia, and water. I 

 should hence consider the green matter as a hydrated silicate of alumina, magnesia, and black 

 oxide of iron, and as being, in all probability, the true green earth, or earthy chlorite of mineralo- 

 gists. The analyses of chlorite hitherto published are so discordant as to prove, either that dif- 

 ferent compounds have been examined under the same name, or that the specimens under exami- 

 nation were very impure. The essential ingredients, however, appear to have been the same as in 

 tiie subject of my analysis. 



"Though the foregoing description applies more immediately to the colouring matter of the 

 green-sand from the vicinity of Folkstone, I have obtained similar results on examining that from 

 Hythe and several other places. Indeed, from the examination of many samples of green-sand 

 collected by Dr. Fitton from various localities in England and France, I believe the colouring 

 matter to be precisely the same in all." 



* See Annates des Mines, 1819, p. G23. < 



