CHAP. XXIX 
THE DERBYSHIRE TOADSTONES 
15 
A wider valley extends along the eastern base of the necks, and slopes 
upward on its east side until it is crowned by a long escarpment of lime- 
stone, which reaches a height of 1000 feet above the sea, or about 100 feet 
above the valley from which it rises. Unfortunately, the bottom and slopes 
of this depression are thickly covered with soil, but at one or two places 
debris of fine tuff may be observed, and at the northern and southern ends 
Fig. 179.— Plan of necks and bedded tuff at Grange Mill, five miles west of Matlock Batli. 
of the hollow well-bedded green and reddish tuff appears, dipping gently 
below the limestone escarpment. This hand of volcanic detritus evidently 
underlies the limestone, and forms most of the gentle slope on the east side 
of the valley. It maybe from 70 to 100 feet thick. That it was dis- 
charged from one or both of the necks seems tolerably clear. Its material 
resembles that forming the matrix of the agglomerate. The general 
/ 3 / 
iiG. 180. — Section across the smaller volcanic neck and the stratified tuff in Carboniferous Limestone, 
Grange Mill. 
1. Limestone ; 2. Stratified tuff intercalated among the limestones ; 3. Agglomerate. 
arrangement of the rocks at this interesting locality is represented in Tig. 
179, which is reduced from my survey on the scale of six inches to a mile. 
A section across the smaller vent would show the structure represented in 
Fig. 180. 
