392 Geological Society: — On the Strata 



When two non-conductors, A, B, are placed in contact, the 

 electricity will not be distributed through the whole of A and B ; 

 and if the displacement is from B to A and parallel to the sides 

 of the cake, the only parts electrified will be the middle and ends 

 of the cake ; the A end of the cake will be positively and the B end 

 negatively electrified ; and if A has a greater specific inductive 

 capacity than B the middle will be negatively electrified ; if it has 

 a less specific inductive capacity than B it will be positively elec- 

 trified. 



I intend to examine more substances, and to endeavour to make 

 some quantitative measurements. The above experiments were 

 made in the Physical Laboratory of Owens College, Manchester; 

 and I have much pleasure in thanking Dr. Stewart, Dr. Schuster, 

 and Mr. Kingdon for the assistance they have given me. 



GEOLOGICAL SOCIETY. 



[Continued from p. 313.] 



March 21st, 1877.— Prof. P. Martin Duncan, M.B., F.E.S., 



President, in the Chair. 



The following communications were read : — 



1. "On the Strata^and their Possil Contents between the Borrow- 

 dale Series of the North of England and the Coniston Plags." By 

 Prof. Eobert Harkness, P.B.S., F.G.S., Professor of Geology in 

 Queen's College, Cork, and H. Alleyne Nicholson, M.D., D.Sc, 

 F.B.S.E., F.G.S., Professor of Natural History in the University of 

 St. Andrews. 



The object of this paper was the investigation of the strata be- 

 tween the great volcanic series of the Lake-district, the Borrowdale 

 rocks, and the sedimentary rocks called Coniston Plags by Prof. 

 Sedgwick. The Borrowdale series, the Green Slates and Porphyries 

 of Sedgwick, are underlain by the Skiddaw Slates, forming the base 

 of the Silurian series, and equivalent in age to the Arenig rocks of 

 Wales, according to their fossil contents. The Borrowdale rocks 

 consist of ashes and breccias, alternating with ancient lavas, and are 

 partly subaerial, partly submarine. They contain no fossils, except 

 in a band of calcareous ashes near the summit of the group, which 

 is followed by the Coniston Limestone, with or without the inter- 

 vention of a bed of trap. The fossils are of Bala types. Some- 

 times this band is recognizable with no traces of fossils except 

 cavities filled with peroxide of iron. The authors regard this as 

 proving the prevalence of volcanic activity in the Lake district up 

 to the later portion of the Bala period. 



The deposits specially discussed in the paper sent, lie, apparently 

 quite conformably, upon the Borrowdale rocks, and are grouped by 

 the authors as follows, in ascending order : — 



1. Dufton Shales. 



2. Coniston Limestones and Shales. 



3. Graptolitic Mudstones or Skelgill Beds. 



4. Knock Beds. 



