Vol. 6$.^ THE TOADSTONES OF DERBYSHIRE. 267" 



Carboniferous Series in Derbyshire. The action commenced 

 near the top of the Mountain Limestone, and continued upwards 

 into 200 feet of the Toredale Shales. The vents occur both, 

 in the Mountain Limestone and in the Yoredale rocks, while the 

 bedded tuffs and lavas are only found in the Limestone-Shales. 



There are four or five vents, one of which is in the Mountain 

 Limestone, another in Mountain Limestone and Limestone-Shales, 

 and the remainder in the Yoredale Shales. Three of the vents 

 occur in what is mapped by the Geological Survey as an inlier of 

 Mountain Limestone, between Bradbourne and Kniveton. The 

 toadstone appeared on the western side of the inlier, but was 

 wanting to the east near "Wigber Low. On the supposition that 

 it was contemporaneous, four faults were introduced to explain 

 its behaviour. 1 



The ground in the neighbourhood is covered with Drift, and 

 the boundary of the limestone is somewhat conjectural. If we 

 adopt the view that these toadstones represent vents, the necessity 

 for at least two of the parallel faults is removed. 



Knivetonwood Cottage. — The oldest vent and the only one 

 entirely in the Mountain Limestone occurs a short distance west 

 of Knivetonwood Cottage. A small elevated piece of ground 

 marks a slight feature in the landscape. The toadstone consists 

 of small blocks of vesicular dolerite, similar to those in the other 

 vents of this area. There are no good exposures, but blocks are 

 to be found at the surface in a number of places. This agglomerate 

 cuts across the strike of the cherty limestones, seen in a small 

 quarry a short distance to the north of it: the beds dip 30° 

 eastward. It also cuts across the strike of the limestones, seen 

 near the Mill-lade on the south, which dip 25° south-westward. 



"Woodeaves Vent. — This vent is about 1 mile north-west 

 of the village of Kniveton, and one field away north-east from 

 Woodeaves Farm ; it is an indented ellipse in area, and may 

 represent either one or two vents. Good sections of the agglomerate 

 and of the Yoredale shales and limestones are seen in the steep 

 and high banks of the two brooks which have cut their way 

 through them. Sir Archibald Geikie, 2 who visited the spot with 

 me some years ago, remarks that the shales and these limestones 

 may be seen much broken and plicated, their curved and fractured 

 ends striking directly at the agglomerate, and that they may be 

 traced to within a yard of the agglomerate. 



The agglomerate cuts across the strike of the beds on the 

 north-west and south, and the vent is partly in the Mountain 

 Limestone and partly in the lower beds of the Yoredale Series. 

 A short distance north of the vent is a limestone-quarry. The 

 beds in it consist of massive limestone with chert- nodules, and a 

 few thin beds of shale. They form a syncline and an anticline, 



1 GeoLSurv. Mem. ' North Derbyshire' 2nd ed. (1887) p. 86. 



2 ' Ancient Volcanoes of Great Britain ' toI. ii (1897) p. 17. 



