Geological Society of London, 237 



Geological Society of London. — I. February 26th, 1868. — 

 Prof. T. H. Huxley, LL.D., F.K.S., President, in the Chair. 

 The following communications were read : — 



1. " Notes on the formation of the Parallel Eoads of Glen Eoy." 

 By C. Babbage, Esq., F.E.S. Communicated by the President. 



Accepting the theory that these roads were formed on the margin 

 of a lake, the author discussed the mode in which this formation 

 took place, objecting to the view of its having occurred through the 

 piling up of pebbles by wave action, or the accumulation of blocks 

 by rain washing them down the hill-side. 



Mr. Babbage expressed his opinion that the material of which 

 the roads are formed was brought down by snow and ice slowly 

 descending tlie hills until arrested on the margin of the frozen lake. 

 On the melting of the snow and ice, it was tranquilly deposited with- 

 out any further descent, and thus lay in a horizontal line. 



In conclusion the author adverted to the theory of the change of 

 isothermal surfaces within the earth, an account of which he had 

 published in the Society's ' Proceedings ' for 1834:, as affording the 

 necessary explanation of the causes which had produced the changes 

 of climate in the district of the Parallel Eoads. 



2. '' On the origin of smoothed, rounded, and hollowed surfaces of 

 Limestone, and Granite." By D. Mackintosh, Esq., F.G.S. 



The author endeavoured to show that smoothed, rounded, hol- 

 lowed, and regularly-perforated surfaces of rock (not glacial, nor 

 mere developments of structure) have been produced, on the Men- 

 dip Hills, by the action of waves charged with sand and stones ; 

 and that deeply-grooved rock-surfaces, near Minera, may have 

 been ground out by stones moved by waves with or without coast- 

 ice. 



3. ''On a striking instance of apparent oblique lamination in 

 Granite." By D. Mackintosh, Esq., F.G.S. 



In this paper the author drew attention to remarkable instances of 

 apparent stratification and oblique lamination in the granite of the 

 Hountor and other rocks of Dartmoor. They seemed to favour the 

 aqueous origin of certain kinds of granite ; though this Mr. Mackin- 

 tosh left an open question. 



4. " On the Encroachment of the Sea in the Bristol Channel." 

 By D. Mackintosh, Esq., F.G.S. 



The object of this paper was to show how the sea denudes a sub- 

 merged land valley by planing it down laterally, Stumps of trees 

 are found under the sea at a distance of at least half a mile from the 

 cliffs near Watchet, with a rocky sea-bottom between. The latter 

 must have been left by the erosive action of the sea, which, to the 

 east of Watchet, has removed the site of a village called Easenton, 

 and encroached at least 200 yards in 150 years. 



5. '' On the two Plains of Hertfordshire and their Gravels." By 

 T. MK. Hughes, Esq., M.A., F.G.S. 



The high ground near Hertford Heath, Brickendon, etc., forms the 

 higher of the two plains which Mr. Hughes described ; out of it a 

 great vaUey has been excavated, the bottom of which forms the lower 



