Geological Society. 419 



obtained, i. e. we know quantitatively the electrical state of the 

 lines at all hours of the day, and seasons of the year ; we are able 

 to localize all faults of all kinds very accurately, and repair them 

 with dispatch ; we test all our telegraphic material, and by it have 

 greatly improved its essential qualities ; we are not groping in the 

 dark any more — we measure and know." 



XLIX. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from vol. vii. p. 442.] 



May 14, 1879.— Prof. P. M. Duncan, M.B., F.R.S., Vice-President, 



in the Chair. 

 rPHE following communications were read : — 

 -*- 1. " Further Observations on the Pre-Cambrian Rocks of Caer- 

 narvon." By Prof. T. M'Kenny Hughes, M. A., F.G.S. 



The author divides these into (1) the volcanic series, (2) the 

 felsitic series, (3) the granitoid series. He traces the former of 

 these, consisting of coarser and finer varieties, from Caernarvon to 

 near Port Dinorwig. Beyond these come the felsite series, which is 

 overlapped by grits and conglomerates as far as the Bangor road, 

 N.E. of Brithdir. Above the latter comes the "volcanic series," well 

 developed in the neighbourhood of Bangor. The author is of 

 opinion that the Cambrian conglomerate, with associated grits, may 

 be traced in the edge of the older massif from Twt Hill, Caernarvon, 

 to Garth Point, Bangor, and that the beds in each of these places 

 and ne Brithdir, recently described as separate, are identical ; 

 also that the bed with purple fragments near TairfTynnon and the 

 Bangor poorhouse are only Cambrian conglomerate faulted down. 

 Further, he considers that the strata of the above three series are 

 fairly parallel throughout, and that they only form three subdi- 

 visions of one great series. 



2. " Notes on the Structure of the Palaeozoic Districts of West 

 Somerset." Bv A. Champernowne, Esq., F.G.S. , and W. A. E. 

 Ussher, Esq., F.G.S. 



The authors confirmed the general accuracy of Mr. Etheridge's 

 views as to the structure of North Devon and West Somerset, but 

 differed from him in ascribing the limestone of Cannington Park to 

 the Carboniferous, both on account of lithological character, the 

 fossils in Taunton Museum said to be obtained from it, and the 

 latitude of its position with reference to the Carboniferous Lime- 

 stone of the Mendip, South Wales, and the steep and flat Holmes. 

 They described four traverses made by them in West Somerset. 

 1st. From Dulverton to Dunster, in which, proceeding northwards, 

 the following beds were encountered: — Culm -measures faulted 

 against Pilton Beds (Upper Devonian) ; Pilton Beds faulted against 

 Pickwell-Down Sandstone (base of Upper Devonian) ; Pickwell- 

 Down Sandstones becoming slaty in passing into Morto slates 



