part 2] THE GEOLOGY OF THE MELD ON VALLEYS. 1 17 



near Castletown Berehaven (County Cork), where sills and dykes 

 clearly intrusive into Carboniferous rocks had proved to be of clastic 

 character. As it was unlikely that 'sills' of this nature could be 

 formed where the beds were horizontal, and the beds were highly 

 inclined as the result of post-Carboniferous movement, the date of 

 the intrusions was an interesting problem. 



The AUTHOR thanked the Fellows for their kind reception of 

 his paper. He had some knowledge of the area in which Dr. Evans 

 .and Dr. Holmes had been working, and he was inclined to agree 

 that repetition did there occur. But, on the Bedaven traverse, he 

 had been unable to find any one bed apparently repeated, if the 

 'dark igneous' rocks were excluded from consideration. And these 

 dark igneous rocks could hardly have been solitary in this respect: 

 other highly characteristic beds would have accompanied them. 

 One broad feature in evidence was that the arenaceous and the 

 calcareous shales met in a well-defined boundary, and neither series 

 trangressed that boundary. The limestone was a well-marked rock, 

 easily identified. The earlier geological survey showed two beds 

 •of limestone, and at some time an attempt was made to open 

 up the southern supposed bed for commercial purposes, with 

 the result that it was proved to exist on the map only. The 

 •error probably arose from the presence of a black chert-like 

 rock, somewhat similar to that which is the constant companion of 

 the limestone. In his paper he had shown that there were three 

 beds of black chert-like rock, but each had its own distinguishing 

 features. 



It appeared to him that, around Dartmoor, the chiastolite-slate 

 had some value stratigraphically, bat, perhaps, rather as marking 

 .a belt than as indicating a definite horizon. 



Replying to Dr. Sherlock, he thought that the Brent-Tor 

 igneous series had a elose kinship with the spilitie series of 

 Plymouth and neighbourhood, but was in no way related to the 

 'dark igneous' rocks of the Meidon Valleys, which were much more 

 .acid. The origin of pillow-lavas in submarine lava-flows could 

 hardly be substantiated in the Plymouth district. A lava-flow 

 over a sea-bed of sand or mud must, he thought, greatly disturb 

 the surface of that deposit; whereas pillow-lavas were found which 

 met the sedimentary rocks in plane surfaces, sometimes coincident 

 with the cleavage, and with no evidence of disturbance. 



Reference had been made to the recurrent liability to catas- 

 trophes such as the storm of August 14th, 11)17. There was no 

 doubt that these storms were more frequent than many thought, 

 but they were usually limited in area and rarely revisited the same 

 spot at any short interval. Tims, in the present instance, there 

 was evidence that the Redaven had never been in such high tlood 

 within the historic period: yet there was a 17th-century record 

 which pointed to a very similar occurrence in the adjacent water- 

 shed; and, within the Author's memory, two Hoods, nearly if 

 not quite as severe, had been known at other points on Dartmoor. 

 He agreed that these phenomena were sufficiently frequent to 



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