Yol. 63.I THE TOADSTONE3 OP DEKBYSHIRE. 259 



250 feet of limestones above the lower lava, and that between the 

 eherty series and this lava there intervene from 180 to 200 feet of 

 massive limestones. 



In Killer Bros.' Quarry (Hoptonwood Stone-Quarry) at Middleton 

 a thickness of 180 to 190 feet of massive limestones is seen above 

 the lava. To the west, towards Middleton, there are from 50 to 60 

 feet of thin eherty limestones above the massive limestones. This 

 gives us about 250 feet of limestones above the lava, which is 

 therefore the lower one of the Matlock district : the upper one 

 having thinned out westwards. In the neighbourhood of the ' Pig- 

 of-Lead ' there is not a continuous section, and the measurements 

 cannot be so accurate as those made in Killer Bros.' quarry. Above 

 the lava are massive limestones to a height of 170 feet, and these are 

 succeeded by thinner limestones with chert and Productas. Allowing 

 for the dip and the hill-slope, there are at least 180 feet of massive 

 limestone-beds between the lava and the eherty limestones. This 

 lava cannot therefore be the upper one, and it is on about the same 

 horizon as the lower lava of the Matlock area. 



I have been unable to find any bed of toadstone on Mininglow 

 Hill, as mapped by the Geological Survey. There are a few erratic 

 blocks of the Calton-Hill type, and these may have been taken to 

 denote the presence of a bed. 



Uncorrelated Lavas. 



On the eastern slope of Masson Hill several isolated patches of 

 lava may be seen. As this is a dip-slope, they probably belong to 

 the upper lava. They are seen at Upperwood, near the Bath- 

 Terrace Hotel, below Cumberland Cavern, and near the southern 

 entrance to the Pavilion. A short distance south-east of Eugshall, 

 on the cart-track from Cromford to Bonsall, a vesicular lava with 

 big felspars can be traced for a short distance, and either disappears 

 under the ridge of dolomitized limestone which extends to Scarthin 

 Nick near Cromford, or is cut out by a fault. The former view is 

 probably correct, because a similar rock with big felspars was 

 exposed a few years ago — when Mr. Lawton's house near Masson 

 Mills was being built. Another small patch of vesicular lava is to 

 be seen in the cart-track mentioned above, about a fifth of a mile 

 north-west of Rugshall, but it is too small to place on the map. 



The exposures of vesicular lava at Greenlow Farm and Aldwark, 

 which belong to one and the same bed, and that near Sacheveral 

 Barn I have mapped as uncorrelated with either of the two main 

 flows of the Matlock area. Near Over Haddon the River Lathkill 

 has cut through a small dome of limestone in which two lavas are 

 seen, separated by about 87 feet of limestone. These, I consider, 

 form part of the upper and lower lavas of this area, although in the 

 absence of proof I have mapped them as uncertain. West of Over 



t2 



