Vol. 54.] IxNT THE CARBOISriFEROUS LlifESTONE OF DERBYSHIRE. 173 



from '70 X "20 mm. to "15 x '05 mm. la some parts of the rock- 

 face the calcite has weathered out, and the quartz-crystals remain 

 loose, but just coherent. Where the rock is much weathered they 

 may be separated by the finger. 



'No. 535, 2 feet below 536, consists almost entirely of quartz-rock. 

 A finer mosaic occurs in a small vein which traverses the slice. 

 Fluor fills small spaces between some of the quartz-grains, and follows 

 part of the course of the vein, not continuously, but in a series of 

 •disconnected portions. 



(c/) Field north of, and adjoining the preceding field. 



In the field immediately north of that in which the old chert- 

 quarry is situated there is an interesting exposure of the quartz-rock. 

 The upper portion consists of a small escarpment of ordinary limestone 

 dipping into the hill in a north-easterly direction. 



Passing over a few yards of grass we come to a bed of limestone, 

 which contains a few quartz-crystals (No. 430). Under this is about 

 6 feet of quartz-rock (jSTo. 529). The upper boundary with the lime- 

 stone is nearly horizontal, the lower is of an undulatory or wavy 

 •outline, the quartz-rock sending down two V-shaped wedges into the 

 limestone below (ISTos. 528, 431 ) ; the lower portions of this are covered 

 with grass, from which a few pieces of quartz-rock project. The lower 

 limestone, close up to and under the quartz-rock, contains a large 

 number of quartz-crystals. These form about 50 per cent, of the 

 rock, and are easil}* visible under a lens when the rock is wetted. 

 There is, therefore, a close association between the quartz-rock and 

 the quartzose limestone. 



No. 529 consists almost entirely of quartz-grains, closely inter- 

 locking and fitting together, and generally elongated. A few have a 

 hexagonal outline, and remain extinct between crossed nicols. Some 

 of them contain a small quantity of calcite. The other constituent 

 is fluor, which is very small in amount, and occupies spaces between 

 the quartz-crystals. 



No. 430 (the limestone above the quartz-rock) contains shell- 

 fragments and a few forarainifera. The quartz-crystals are not 

 numerous. They are idiomorphic, and combinations of the prism 

 and double pyramid. The majority are clear, but some contain a 

 small quantity of calcite. 



No. 528 (6 inches below the lower boundary of the quartz-rock) 

 is similar to the preceding, but contains a greater number of fora- 

 minifera, one of which is penetrated by a quartz-crystal. 



No. 431, about 7 inches below the quartz-rock, is a limestone, 

 containing few foraminifera and numerous quartz-crystals with 

 sharp outlines. Some of them include a small quantity of calcite. 

 Several small veins or strings of quartz traverse the slide in such a 

 manner that the quartz-crystals are sometimes aggregated along 

 tortuous lines, which are not always continuous, but interrupted. 

 One of these bifurcates, and the branches run together again after 



