156 Mr Mayall, On Current Sheets, especially [Feb. 26, 



and were deposited in narrow bays in the Upper Cretaceous 

 sea of Southern and Central Europe on the Northern flanks of 

 the Eastern Alps. 



Probably towards the close of Upper Cretaceous times the 

 Southern area of the Gosau district was cut off from free com- 

 munication with the sea, so as to constitute a lake-basin, in which 

 the upper unfossiliferous marls were deposited. 



From the stratigraphical position of the beds, and the oc- 

 currence of a calcareous conglomerate at their base, it is evident 

 that the older secondary rocks of the Eastern Alps on which they 

 rest had undergone elevation and denudation with a considerable 

 amount of earth-movement, accompanied by contortion and plica- 

 tion, previous to the period of depression when the Gosau beds 

 were deposited. During the deposition of the latter, the Eastern 

 Alps probably existed as fairly high land along the central portion 

 of the chain, with a very irregular coast -line along its Northern 

 flanks. At the close of Cretaceous times there was considerable 

 elevation, which was followed by depression in the Eocene period 

 at the time of the deposition of the Nummulitic Rocks and the 

 Flysch, Then followed the period of the great Alpine uplift, 

 a movement intense in the Western portion and gradually dying 

 out towards the East in the direction of the Vienna Basin ; and 

 it is to this period that the present magnitude of the mountains is 

 chiefly due, and the present isolated and elevated position of the 

 several small areas occupied by the Gosau Beds. 



February 26, 1894. 



Professor Hughes, President, in the Chair. 



Philip Lake, M.A., St John's College, was elected a Fellow 

 of the Society, and W. H. Rivers, M.D. (Lond.), St John's College, 

 was elected an Associate. 



The following Communications were made to the Society : 



(1) On Current Sheets, especially on Ellipsoids and A7ichor- 

 Rings. By R. H. D. Mayall, B.A., Sidney Sussex College, 

 Cambridge. 



In the following paper I propose to consider the electric 

 currents induced in thin sheets of a conducting substance by 

 the variation of a magnetic field in which they are placed. For 

 those particular cases when the conducting sheet takes the form 

 of an infinite plane, a sphere, an ellipsoid, or a cylinder whose 

 cross-section is of the second degree, the results have been 

 worked out by several different investigators with slightly 

 different methods and are to be found in various scientific 



