492 Geological Society : — 



forms of the electrical jar. The author could not, at least, discover 

 any material difference in the results, and concludes that if the first 

 forms of the electrical jar with an internal coating of water had been 

 continued, we should have had hut small experience of the effects of 

 artificial electrical discharge on metallic wires. 



Imperfect conducting substances employed as coatings to the elec- 

 trical jar have very similar but very exaggerated effects. "With coat- 

 ings of paper we have a striking example of retention of charge. A 

 jar exposing 5*5 feet of coated glass, first coated with metal and sub- 

 sequently with paper, gave the following results under a charge of 

 100 measures. 



Exploding distances, as in the former case, nearly the same, being 

 •23 and *25 ; attractive forces or intensity also nearly the same, 

 being 158° and 160°; residual measures with the metal coating 2*5 

 measures, or about the ^-th of the total charge; with paper coating, in 

 some experiments 80 measures, or about -p^ths of the total charge, so 

 that the residual charges with metal and paper are as 1 : 32. Thermo- 

 electric effect for metal coating 8°, for paper coating nothing. It 

 appears from these and similar experiments, that the interposition of 

 imperfect conductors between the coating and the glass of the Ley den 

 jar must necessarily impair its efficiency, and change its electrical 

 indications, especially when of any considerable thickness. Three 

 turns of common linen interposed between the outer coating and the 

 glass reduced the force of discharge from 11° to 6°, nearly one-half, 

 whilst the residuary or retention of charge is considerably increased : 

 this question, as bearing in some degree on the retention of charge by 

 the electric cable, may not be undeserving of further investigation. 



GEOLOGICAL SOCIETY. 



[Continued from p. 414.] 



March 19, 1862. — Prof. A. C. Ramsay, President, in the Chair. 



The following communications were read : — 



1. " On the Sandstones, and their associated deposits, in the 

 Valley of the Eden, the Cumberland Plain, and the South-east of 

 Dumfriesshire." By Prof. R. Harkness, F.R.S., F.G.S. 



Having defined the area occupied by these sandstones, breccias, 

 clays, and flagstones* and referred to the published memoirs in which 

 some notices of these deposits have been given by Buckland, Sedg- 

 wick, Phillips, and Binney, the author described, 1st, a section near 

 Kirkby- Stephen, across the vale of the Eden, where two breccias, 

 separated by sandy clay-beds, underlie sandstones of considerable 

 thickness ; 2ndly, a section across Eden Vale from Great Ormside 

 to Roman Fell, in which the breccias, associated with sandstones, 

 form a mass 2000 feet thick, and are succeeded by thin sandstones, 

 shales (with fossils), and thin limestone, altogether about 160 feet, 

 and next by sandstones 700 feet thick. This is the typical section ; 

 the fossiliferous shales are regarded by Prof. Harkness as equivalent 

 to the Permian Marl-slate of Durham ; they contain (at Hilton Beck) 

 remains of Conifer a, Neuropteris, Sphenopteris , Weissites (?), Cau- 

 lerpites selaginoides (?), Cupressites Ullmani (?), Voltzia Pkillipsii (?), 



