[ 135 ] 



' XV. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxiii. p. 468.] 



February 9, 1887.— Prof. J. W. Judd, E.R.S., President, 



in the Chair. 



npHE following communications were read : — 



-*- 1. " Evidence of Glacial Action in the Carboniferous and Hawkes- 



bury Series, New South Wales." By T. W. Edgworth David, Esq., 



E.G.S. 



After giving a tabular statement of the sequence of rocks connected 

 with the coal-bearing beds in New South Wales, the Author passed 

 in review the notices by previous observers of glacial action in the 

 Carboniferous beds of that country, terminating with the discovery 

 by Mr. K. D. Oldham of polished and striated boulders in fossiliferous 

 marine beds of Carboniferous age at Branxton. The author had since 

 found another extensive deposit of similar beds at Grass-tree near 

 Musclebrook, 28 miles N.W. of Branxton, and described the section 

 there exposed in a railway-cutting. A fine calcareous sandy shale, 

 reddish to greenish brown in colour, was crowded with round and 

 subangular fragments of rock, from pebbles no larger than marbles 

 up to a third of a ton in weight. The surfaces of these fragments 

 were in many cases ground and scratched. The parent rock of some 

 of the boulders was 30 miles distant. 



The evidence of ice-action in the Triassic Hawkesbury series was 

 also described. This evidence was twofold, and consisted of the 

 disrupted angular fragments of shale first observed by Mr. Wilkin- 

 son, and of contemporaneously contorted current-bedding, of which 

 no account had previously been published. The contortions were 

 represented on a diagram, and attributed to a lateral thrust such as 

 would be produced by the grounding of floating ice. 



The discovery by Mr. Wilkinson of polished and striated boulders 

 in some gold-bearing conglomerates believed to be of Siluro-Devo- 

 nian age was also noticed. 



2. " The Terraces of Eotomahana, New Zealand." By Josiah 

 Martin, Esq., F.G.S. 



The Author, after deploring the recent calamity, proceeded to de- 

 scribe the White Terrace. Its origin, the Terata Geyser, was situated 

 in a crater-like escarpment near the centre of a conical hill of 

 steaming and partially decomposed felspathic tuff on the south-east side 

 of the warm lake, Rotomahana. The Terrace was divided into : — 



1. The Upper Terrace, with its long horizontal lines of cups, 

 steaming and overflowing with hot water. 



2. The Middle Terrace, with its massive steps and shaggy fringes, 

 without basins or receptacles for the overflow. 



3. The Lower Plateau, a series of shallow basins and wide, level 

 platforms. 



The great cauldron and the action of the Geyser were described 

 in much detail. The following analysis of the water was given in 

 grains per gallon. 



