114 DR. CH. CALLAWAY ON THE TJNCONFOKMTTIES BETWEEN 



would prove too much ; for I have found similar flakes low down in 

 the great grits of the so-called " Moiiian'' on the southern slopes of 

 the Ashes Hollow. I need hardly state that they are devoid of 

 significance. 



In pointing out the insufficiency of the above attempt to refute 

 the received views, I do not wish to prejudge issues outside the 

 present enquiry. I have not critically studied the whole of the 

 Longmynd area, and must leave some points for future research. 



(b) Presence of Rolled Fragments of Volcanic Rock in the so-called 

 " Monian " Series. — These are not very common ; but they exist. 

 One good specimen I found in the green grit of Ashes Hollow. It 

 is a well-rounded pebble of about one inch in diameter. The 

 material is certainly volcanic. In the field it looked like felsite, 

 and under the microscope it appeared to me to show a micro- 

 crystalline structure. Prof. Bonney leans to the opinion that it is 

 allied to obsidian, though he does not absolutely exclude the alter- 

 native of a highly altered mudstone. As there are no lava-flows in 

 the Longmynd Series, and, so far as I know, no mudstones resembling 

 felsite, it would seem that such pebbles must be derived from an 

 earlier formation. 



3. The Conglomerates and Grits. 



Prof. Blake truly remarks {op. cit. p. 408) that the age of these 

 conglomerates and grits is " of supreme importance in connection 

 with the general interpretation of the district." With equal 

 accuracy, he adds that they have been taken by the present writer 

 to be " part of the volcanic series." He is not, however, correct 

 in saying that I regard them as proving " the clastic origin of the 

 latter." It is true that a grit contains the evidence of its own 

 " clastic origin " ; but it certainly does not carry with it the genesis 

 of any lava-flows that may be associated with it. 



Prof. Blake contends that these clastic rocks do not belong to 

 the Uriconian, but are outlying patches of the " Cambrian " strata 

 which form the western half of the Longmynd Series. He mentions 

 examples occurring on the Cardington massif, on Caer Caradoc, and 

 on Charlton Hill. I will deal with these seriatim. 



(a) The Cardington Massif. — Certain patches of grit at or near 

 the Gaer Stone are said to be "superficial," but no evidence is 

 ottered in support of that opinion. One of the numerous patches 

 that ie near Willstone Hill is noticed ; but again its " Cambrian " 

 age is assumed. I have examined a large number of exposures of 

 grit in the western part of the Cardington mass, but could obtain 

 no evidence of unconformity. Parther east, however, there is clear 

 proof in at least two localities that this grit is intercalated in the 

 volcanic series. One mass occurs a little more than half a mile 

 east of the Gaer Stone in the ravine which opens on to the Hope- 

 Bowdler road, opposite " The Yells." This rock is of the usual type^ 

 as described by Prof. Bonney in an appendix to my 1879 paper *, 



* Quart. Journ. Geol. Soc. toI. xxxr. p. 607. 



