518 DK. C. CALLAWAY ON THE LONGMYNDIAN [Aug. ICJOOy 



II. The Longmyndian Inlier at Huntley. 



It is more than thirty years since Murchison recognized the 

 presence of rocks similar to those of the Longmynd in a quarry west 

 of Huntley. He writes l : — 



' In approaching the higher ground, the first rock which is observed to jut 

 out from the plain of the New Bed Marls, has all the aspect of the Cambrian 

 rocks of the Longmynd. It is a hard, siliceous, close-grained, dark-grey,, 

 schistose stone with quartz-veins, and is quarried for the use of the roads.' 



This description requires some modification. The rock is ' schis- 

 tose ' only in the sense in which an ordinary grit or shale is 

 ■ schistose.' Nor is it predominately ' quartzose.' A typical speci- 

 men of the rock, cut for the microscope, is seen to consist mainly 

 of felspar, with quartz in quite subordinate proportion. The former 

 includes both orthoclase and plagioclase. Some of it is in unbroken 

 prisms, the remainder being in irregular angular fragments. The 

 quartz also is in angular bits. The slide contains a fair proportion 

 of a black opaque substance in irregular particles, many of which 

 contain minute elongated prisms of felspar, suggesting a partly 

 decomposed dolerite. 



This grit, though it suggested to Murchison, as it did indepen- 

 dently to myself long afterwards, a resemblance to the Longmynd 

 Series, 2 does not under the microscope present a very close similarity. 

 Judging from the slide examined, the rock is wanting in the bits of 

 rhyolite which are so characteristic of typical Longmyndian, and it 

 is distinguished by a greater abundance of felspar. Some hand- 

 specimens of the rock are, however, less felspathic. The angularity 

 of the quartz is a feature common to the Huntley rock and to the 

 typical Longmyndian grit. The black grains are not characteristic 

 of the type, but I have seen them in a slide from Haughmond Hill. 

 The shaly beds associated with the grits are also suggestive of the 

 Longmyndian of Shropshire, being more indurated than ordinary 

 shales. 



The section exposed in Huntley Quarry presents a thickness 

 of about 80 feet, massive grits predominating over the shaly bands. 

 The beds stand almost vertical, with an easterly dip, but towards 

 the bottom they curve round westward, so that they probably form 

 part of a fold (see the appended section, p. 519). The rocks may be 

 traced across the strike for about 200 yards. They form a small hill 

 projecting like a promontory towards the south, with the Trias faulted 

 against the eastern base, and a hollow dividing the ridge from the 

 May Hill Sandstone on the west. 



That the Huntley mass is not Silurian appears evident from its 

 dissimilarity to the adjacent May Hill Series. The nearest ex- 

 posure of the latter occurs in a small quarry in a garden, about 

 200 yards to the south-west. The rocks are highly quartzose, with 



1 ' Siluria ' 4th ed. (1867) p. 99. 



2 [Phillips, Mem. Geol. Surv. vol. ii, pt. i (1848) p. 183, also mentions the 

 older rocks of Huntley Hill when dealing with the Caradoc Sandstone, but he 

 does not remark on their similarity to the Longmyndian.] 



