xlvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Silurians. The scantiness of palaeontological evidence renders the 

 exact determination of their equivalents peculiarly difficult. 



In Scotland the subject of glacial phsenoraena continues to be 

 discussed and investigated with unabated interest. ]\Ir. Robert 

 Chambers has been actively engaged in the collection of facts con- 

 cerning the glaciation of Britain and the attendant phsenomena. His 

 views have been communicated at some length to the Royal Society 

 of Edinburgh, and may be found printed at full in the fifty-fourth 

 volume (for 1853) of the Edinburgh New Philosophical Journal. 

 He recalls attention to the evidences of the presence of local systems 

 of glaciers, of ordinary and typical constitution, in the mountain 

 districts of North Wales, Cumbria, and. Scotland, and notices fresh 

 instances of this phsenomenon. From it, however, he distinguishes 

 the evidences of what he considers glacial action of a more general 

 kind, manifested in Scotland, in every part of the Highlands, and much 

 of the Lowlands, in the rounding, smoothing, and striation of rocks, 

 generally in the line of valley, and also in elevations to as much as 2000 

 feet above the sea-level. Professor Ramsay had previously demon- 

 strated two distinct epochs of glaciers in North Wales. The direction 

 of the icy agent in these cases Mr. Chambers maintains to have come 

 from the north-west, and to have acted with little regard to the inequa- 

 lities of the surface. He interprets the phsenomena as indicating the 

 passage over wide areas of an abrading agent, at the same time plastic 

 and of volume sufficient to fill valleys several miles in breadth, and from 

 one to two thousand feet in depth, and he maintains the probability 

 of this agent being ice much water- charged and more mobile than as 

 presented in an ordinary glacier. He holds the power of the de- 

 nuding force of this agent to have been very considerable. The older 

 boulder clay he regards as the detritus of this general glaciation, 

 which he believes to have taken place at a period anterior to the 

 epoch of the northern drift, which itself preceded the epoch of 

 local glacier systems. There is much that is highly interesting and 

 suggestive in Mr. Chambers' paper, even though we may not be in- 

 clined to go along with him unhesitatingly in his speculations. The 

 subject of the ancient glacial phaenomena of Britain, Scandinavia, and 

 America, is evidently fast advancing towards new combinations, and 

 the multiplication of local observations, of which many good examples 

 are contributed by Mr. Chambers, will most effectually promote our 

 progress towards definite conclusions. In the mean time those who 

 occupy themselves with these inquiries should closely study the 

 admirable and beautiful work on the existing glaciers of Norway, 

 just contributed to science by Professor James D. Forbes of Edin- 

 burgh. The thorough knowledge and science of the author, his 

 great experience, his searching and logical treatment of his subject, 

 and the excellence of his style render all his works on this difficult 

 matter models and guides. 



The condition of the surface of the emerged land of the Scottish 

 area during the epoch of general glaciation, the existence of which is 

 inferred by Mr. Chambers, must have been very comparable with 

 that noticed by Dr. Rink, in his late paper " On the Continental Ice 



