512 Notices of Memoirs — H. Bolton — Boulders near Malton. 



incipient foliation, presenting a slightly gneissoid appearance, and 

 apparently a much sheared diabase. The association of the chloritio 

 rocks with the mica schists is of as intimate a nature as that of the 

 volcanic materials with the unaltered slates to the north. From 

 these facts it seems evident that the chloritic series is nothing 

 more than a Devonian volcanic group, of which the Torcross, Stoke 

 Fleming, Dartmouth, and Kingswear coast tuffs and diabases were 

 either sporadic offshoots or evidences of more or less contemporaneous 

 local vulcanicity. 



The more evident crinkling of the mica schists in contact with 

 the chloritic group seems to be due to their comparative softness and 

 greater fissility during the crumpling and contraction to which both 

 were subjected. 



The comparative suddenness of the transition from unaltered to 

 more or less highly altered rocks may be explained by the lessening 

 of strain (in receding from the harder masses of ancient rocks, 

 against which the beds were jammed), being coincident with the 

 thinning out of the volcanic materials northward, and furthermore 

 favoured by the soft character of the grey slates with limonitic 

 interfilmings which everywhere bound the northern chloritic band 

 on the north. It is not the author's present purpose to enter more 

 particularly into the stratigraphy of this interesting region, which is 

 not yet thoroughly worked out. It only remains to acknowledge the 

 prior claim of Mr. Somervail to the suggestion of the identity of the 

 Devonian diabases with the chloritic rocks.' 



Xll. — Note on Boulders at Darley, near Matlock, Derbyshire. 

 By Herbert Bolton. 



DUEING the excavation for a small lake close to the Midland 

 Eailway Station at Darley, near Matlock, a cluster of fifteen 

 boulders were exposed, the size of several being sufficient to justify 

 an examination. The boulders lay in a bed of Boulder-clay which 

 had a thickness of nine feet. 



The upper part of the clay was of a strong yellow colour and 

 very stiff. Below, the colour varied from yellow to brown and red, 

 and pockets of sand were common. 



Only two boulders were rounded, the rest being sub-angular, on 

 their upper half, and fairly angular on the lower. 



All the boulders consist of gritstone identical in character with 

 the Chatsworth grit of the adjoining hills. 



No striations occur in the boulders, but this may be due to the 

 original surface having crumbled away. 



A series of parallel and shallow grooves occur on the side of the 

 largest boulders, and a deep hollow has been scooped out of its 

 southern face. 



The major axis of the undisturbed boulder was approximately 

 north and south, the general direction of the cluster being 8° west 

 of noi-th. The blocks were arranged in the order of their weight 



1 The views above expressed are those to which the author himself has been led, 

 but they have not yet been fully considered and adopted by the Geological Survey. 



