832 Reports and Proceedings — Geological Society of London. 



and biotite-gneisses of tlae Central Highlands, without anywhere 

 reverting to the approximately unaltered condition which they 

 exhibit to the south-west. The sills become granulitized and 

 partly recrystallized, with biotite and garnets. 



These rocks, which occur on the strike of the Central Highland 

 schists, ai'e linked with the latter by the persistence of the Loch 

 Awe rock-types, including the boulder-bed, which is regarded as 

 having a definite stratigraphical position. It is true that when 

 traced along the strike the metamorphism increases rapidly towards 

 such granite-masses as that of Ben Cruachan, but the same type of 

 metamorphism continues into the Central Highlands, and into 

 regions so remote from the granite that the author is driven to 

 believe that " without the presence of the Cruachan granite the 

 increasing metamorphism, though possibly more gradual, where 

 that granite now occurs, would have been equally apparent." 

 Evidence of metamorphism when the rocks are traced across their 

 strike is also adduced. 



Although the author does not go veiy fully into the question of 

 the causes of the progressive metamorphism exhibited in tracing 

 these rocks towards and into the Central Highland schists, he had 

 reason to suspect that " the intense regional type of metamorphism 

 was linked with the same phenomena that afterwards resulted in 

 the irruption of the granite-masses." 



III.— June 7, 1899.— W. Whitaker, B.A., F.K.S., President, 

 in the Chair. 



Mr. F. A. Bather, in exhibiting, on behalf of Mr. R. D. Darbishire, 

 a pebble found in gravel near St. Margaret's, Bowdon (Cheshire), 

 said that it consisted of liver-coloured quartzite, and no doubt once 

 formed part of the Bunter Pebble-beds, though these do not occur in 

 the immediate neighbourhood of Bowdon. It had been reported to 

 Mr. Darbishire as found in river-gravel ; but reference to Sheet 

 80 N.E. of the Geological Survey map (lin. Drift) showed that the 

 deposit was Drift of alleged glacial origin. The specimen was an 

 exceedingly perfect and characteristic example of the pyramid- 

 pebbles or • Dreikanter,' such as are found in the ' Diluvium ' of the 

 North German plain, and in other parts of the world from the 

 Cambrian to rocks now forming, but hitherto not recorded from 

 England. These have been explained as due to : (1) human agency, 

 (2) glacial action (Theile), (3) compression in a pebble-bed 

 (' Packungstheorie' of Berendt), and (4) action of wind and sand. 

 The last explanation was the only one tliat met the facts of the case, 

 as proved by A. von Mickwitz (Mem. Soe. Imp. Mineral. St. Petersb., 

 ser. ii, vol. xxii, pp. 82-98, pis. viii, ix, 1887). 



In illustration of his remarks, Mr. Bather exhibited a series 

 of specimens which had been collected under the giiidance of 

 M. Mickwitz from the locality described by that author on the 

 shore of the Obersee, south of lieval, Esthonia. They confirmed the 

 statement that the three sides of the pyramids lay at right angles 



