36 NOTliS ON THE GEOLOGY OF IjERBVSHIRE. 



Near Newhaven, Brassington, and Harbro' occur some purple 

 and white fire-clays and sands in irregular hollows in the limestone 

 as much as 100 yards across, and of unknown depth. The 

 memoir states that the presence of quartz pebbles points to a 

 portion of the deposit having been derived from the Kinder Scout 

 Grit, and that a large part of the material is due to the decom- 

 position of chert and sandy or argillaceous limestone. The sand 

 consists almost entirely of quartz ; a comparison of the grains with 

 those in the Grit and the insoluble residues in the limestone might 

 throw some light on the subject. In the Longcliffe pit is a lignite, 

 and it might be worth while to look near it for seeds which would 

 determine the plant from which the wood came. 



In February, 1888, I heard a paper read at the Geological 

 Society by Mr. VVethered, on "Insoluble residues obtained from 

 the carboniferous limestone series at Clifton." The specimens of 

 limestone were placed in hydrochloric acid, the residue washed, 

 and then examined under the microscope. The residue of the 

 lower limestone shales consists mostly of detrital quartz, with 

 fragments of tourmaline, zircon, and felspar, occasionally 

 associated with amorphous and chalcedonic silica. In the middle 

 limestones the proportion of chalcedonic silica, containing sponge 

 spicules and casts, increases, that of detrital quartz decreases, 

 micro-crystals of quartz, amorphous silica, and less frequently 

 pyrites, tourmaline and zircon occur. Towards the top of the 

 middle limestones the proportion of detrital quartz increases, and 

 the deposition of secondary silica on the grains becomes less 

 marked until the calcareous beds become replaced by the Mill- 

 stone Grit. Mr. Wethered concluded that tlie greater portion of 

 the limestone at Clifton was deposited in the form of material not 

 unlike that of the chalk and calcareous mud, now being deposited, 

 in which siliceous organisms occur, and was in fact a Paleozoic 

 chalk. The calcareous organisms he hoped to deal with later. 

 Such a method might be applied to the Derbyshire limestone, and 

 the work would not present much difficulty. Little chemical 

 apparatus would be required, and a microscope magnifying about 

 40 or 80 diameters, with a polariscope attached, would be sufficient. 



