Geological Society. 477 



about a diameter, and n being equal to t divided by the moment of 

 inertia of a circular section about the centre. The "resistance to 

 compression/' k s is then determined by the formula 



-L=3__I 



3/£ - M n 

 and the " ratio of the lateral contraction to longitudinal extension/* 

 r, by the formula 



M . 



0= — 1. 



2n 

 The values found for the flint-glass rod experimented on were, in 

 grammes' weight per square centimetre, 

 M= 6 14,330,000, 

 n =244,170,000, 

 k =423,010,000, 

 a = -258. 

 The mode of experimenting is somewhat similar to that by which 

 KirchhorT investigated the value of a for steel and brass ; but there 

 are several points of difference, especially this— that the portion of 

 the glass rod, whose flexure and torsion are measured, is sufficiently 

 distant from the places where external forces are applied, to eliminate 

 the local irregularities produced by their application. 





GEOLOGICAL SOCIETY. 

 [Continued from p. 401.] 

 March 7, 1866. — "WaringtonW. Smyth, Esq., President, in the Chair. 

 The following communications were read: — 



1. " Documents relating to the formation of a new island in the 

 neighbourhood of the Kameni Islands." By St. Vincent Lloyd, 

 Esq., H.M. Consul at Syra, A. Delenda, Esq., Consular Agent at 

 Santorino, and M. Decigala. 



In these documents it was stated that on or about February 1st 

 the sea in the neighbourhood of the Kameni Islands, in the centre of 

 the crater forming the harbour of Santorino, began to show signs of 

 volcanic action, and that the result has been the formation of a new 

 island, which has since become nearly joined to the south of the 

 island Nea Kameni. Details of the volcanic phenomena observed 

 up to February 7th were given in the letters from Messrs. Lloyd and 

 Delenda; and in the impression of 'La Grece' newspaper of 

 February 15th, M. De'cigala gave an account of the further progress 

 of the upheaval and increase of the new island, which he had named 

 " George the First." 



2. "On the Carboniferous Slate (Devonian Rocks) of North 

 Devon and South Ireland." By J. Beete Jukes, Esq., M.A., 

 F.R.S., F.G.S. 



Mr. Jukes gave a sketch of the geological structure of the south- 

 west of Ireland, tracing the Old Red Sandstone and Carboniferous 

 Limestone from Wexford through Waterford into Cork, and show- 

 ing that some thin beds of black shale which intervened between 

 those groups on the east expanded westwards until they acquired 



