258 MR. H. H. ARNOLB-BEMBOSE ON [Allg. 1907, 



Dale, between Matlock Bridge and Matlock Bath, it is brought up 

 by the anticline and seen at the bottom of the valley. 



It may be traced from Church Street, Bonsall, near Herbert Lodge 

 to the summit of Masson Hill by Low Farm to Salter's Lane. 

 The limestones above it are often dolomitized. The outcrop then 

 turns westward under the escarpment of coralline limestone which 

 dips rapidly down the dip-slope towards Darley Dale. At Tearsall 

 Farm, and for a distance of nearly a mile west of that place, the lava 

 is succeeded by a bed of tuff. A good section of the tuff is seen close 

 to Tearsall Farm. Several feet of it are shown dipping with the 

 limestone which rests upon it : it is well laminated. The lava can 

 be followed farther west underneath the escarpment of limestone 

 which here has become dolomitized, across the road from Winster 

 to Grangemill, and also across that from Winster to Pike Hall. 

 For the next mile and a third all signs of it are lost : I have 

 therefore dotted in the boundary-lines. About a third of a mile 

 north of the road from Winster to Pike Hall a vesicular toadstone 

 is seen : this I take to be part of the lower lava. It runs on in 

 a northerly direction across Gratton Dale, and then thins out. 

 A good exposure of it is seen in the dale, and about 250 feet of 

 limestones are seen above it. Hopkins states that 



* it is easily traced just across the dale, beyond which the basset suddenly ceases, 

 and no further trace whatever can be found of it.' (Op. jam cit. p. 32.) 



This appears to be the westernmost extension of the lower lava 

 of the district. 



At Dunsley Mill, a bed of vesicular lava is seen to occupy the 

 bottom of the valley as far as the ' Pig-of-Lead ' public-house ; it 

 then mounts both sides of the Via Gellia, and may be traced as far 

 as Hollow-church Way, where it is probably cut off by a fault. 

 The lava may be followed under the limestones of Middleton Moor 

 through the village of Middleton in a north-westerly direction ; 

 the outcrop then turns southward, and may be followed through the 

 top of Hoptonwood Quarry to the High-Peak Railway, a short 

 distance west of Hopton Tunnel : it crosses the railway-cutting. 

 I have been unable to find it for the next half-mile, as mapped 

 by the Geological Survey ; and it probably thins out. It may be 

 found in the opposite direction to the foregoing, south of Middleton, 

 as far as Messrs. Killer Bros/ quarry (Hoptonwood Stone-Quarry). 

 It is seen near the top of the quarry, and at its southernmost point 

 is cut off by a fault ranging north-north-west and south-south-east, 

 and brought down to a lower level near the bottom of the quarry. 

 It is then carried beneath the limestones, and is cut out by the 

 Gulph Fault, which ranges from Middleton to Wirks worth. In the 

 lower part of the quarry the toadstone was seen faulted against the 

 limestone. 



I have mapped the Middleton and ' Pig-of-Lead ' lavas as part of 

 the lower lava of he Matlock area, for the following reasons. From 

 the section tabulated below (p. 261) it appears that there are about 



