THE CROSS PELL INLIER. 503 



rocks of the Horrowdale Series, but into tliis (]uestion we cannot 

 enter here. Mr. Marker has examined slides of rocks from the 

 Milburn (xroup of Wytlnvaite and the neii^hbourhood, and his 

 description will be found in Appendix I. to this paper. 



Though all the bedded rocks on the eastern side of the main 

 inlier are either shales or lavas and ashes intcrstratified with shales, 

 we do get another group of volcanic rocks on the cast side of the 

 Knock rike-Flagdaw Fault in a subsidiary inlier which lies east of 

 the village of Jklelmerby, and which is separated from the main 

 inlier by a band of Carboniferous conglomerate, a few score yards 

 in width, abutting against the Xew Red Sandstone. At the south 

 «nd of this small inlier a group of basic rocks, consisting of ashes 

 and porphyritic and vesicular lavas, is separated from a group of 

 rhyolitic rocks by the above-mentioned fault. Unfortunately, 

 owing to the intervention of the Carboniferous beds, which are 

 here faulted down, the relationship of the basic lavas and ashes to 

 the shales farther south is not seen. That these basic volcanic 

 rocks are the equivalents of the Eycott lavas was recognized by 

 Mr. Goodchild *, and a porphyritic rock, of which a beautiful 

 specimen from Eakc Brow is preserved in the Museum of Practical 

 Geology (London), is quite similar to one of the well-known porphy- 

 ritic Eycott lavas f. Unfortunately this group of rocks is flanked 

 by (Carboniferous rocks or by faults on all sides, so that its true 

 relationship to the other rocks of the district is not shown. 



The rocks of the eastern half of the inlier are also marked by the 

 intrusion of a considerable quantity of igneous matter, and as an 

 examination of the intruded rocks is of importance as throwing 

 light upon the general sequence of events in the district, we may 

 give a brief account of their development. 



The principal masses occupy the prominent ridge of Cuns Fell, 

 and the slopes of Thack Moor. Cuns Fell is formed mainly of 

 diabase running in a general north-east to south-westerly direction, 

 and sending oif a considerable tongue to the south. On the east 

 side of the hill, in Ousby Dale, much felsitic rock is associated with 

 the diabase, under such couditions that it is difficult to make out 

 the relations of the two rocks, though on the summit of the hill a 

 felsitic dyke is undoubtedly intrusive in the diabase. Whether or 

 no the felsitic rocks are the newer, they probably belong to the 

 same general period. That they were intruded before the end of 

 Silurian times is rendered probable by the absence of cleavage in 

 the highly baked shales below the mass, and b}' the existence of a 

 schistose structure in the diabase, seen at the spring in Ousby Dale. 

 This appears to indicate that they were intruded previously to the 

 exertion of the pressure which has folded and cleaved the rocks, 

 and we arc inclined to believe that the masses are of the same 

 general age as the volcanic material which forms the Borrowdale 

 series, and are related to the volcanic outpourings of that group. 



* Trans. Cumb. and Westm. Assoc, vol. ix. (1884) p. 183. 

 t For notes on these rocks see Appendix I. 



