16 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 20, 



whether the place of derivation of most of the blocks was Scotland. 

 Besides the rocks mentioned, he had found fragments of Magnesian 

 Limestone and columns of Poteriocrinus. He could not agree with the 

 authors as to the physical geography of Britain during the Upper- 

 Greensand period. He considered that it was from the denudation 

 of the great barrier mentioned in the paper that much of the mate- 

 rial of the Upper Greensand was derived, and disputed the value 

 of conclusions as to climate founded on so small an area of induction. 



Mr. J. F. Walker did not agree with the authors as to the absence 

 of large ammonites in the Cambridge Greensand, and of fossils in the 

 Gault of the neighbourhood of Cambridge ; the latter had been found 

 by Mr. Keeping at Upware. He inquired in what state of combina- 

 tion the phosphoric acid was supposed to be brought from Scotland. 



Mr. Sollas, in reply, stated that the scratches referred to by 

 Mr. Seeley could not be of modern formation, since they were in 

 many cases partly covered by incrusting Plicatula sigittum, and 

 pointed out the difficulty attending the supposition that the blocks 

 were derived from any other than a northern source. He thought 

 that the large ammonites were derived from a lower bed in the 

 Gault than that from which he had supposed a large portion of the 

 Upper-Greensand fossils had been derived. He considered that the 

 phosphoric acid had been conveyed along the sea-bottom in a cold 

 current, perhaps as a calcic phosphate. 



Mr. Jukes-Browne also replied, and drew attention to a section 

 he had prepared, which showed that the London and Harwich anti- 

 clinal had been covered with a great thickness of Gault at the time 

 of the deposit of the Upper Greensand. 



Prof. Ramsay, in winding up the discussion, expressed an opinion 

 that the forms of pebbles of glacial origin might be recognized by 

 an experienced eye even though the striae had been worn off, and 

 that some of the pebbles exhibited showed traces of such an origin. 

 He called attention to the fact that the deposit of glaciated pebbles 

 in any particular locality did not in any way involve the existence 

 of arctic conditions at that spot, though they might exist elsewhere. 



November 20, 1872. 



Lieut. Charles Cooper King, Royal Marine Artillery, Royal Mili- 

 tary College, Sandhurst, and H. L. Florence, Esq., 16 Christchurch 

 Road, Streatham Hill, were elected Fellows of the Society. 



The following communications were read : — 



1. On the Geology of the Thunder-Bay and Shabendowan Mining- 

 districts on the North Shore of Lake Superior. By H. 

 Alleyne Nicholson, M.D., D.Sc, M.A., F.G.S., F.R.S.E., &c, 

 Professor of Natural History in University College, Toronto. 



Having recently had an opportunity of accompanying an exploring 

 party to the north of Lake Superior, I take this occasion to give a 



