TRANSACTIONS OF SECTION C. 475 
Grenville limestones represent chemical precipitates from the Keewatin 
ocean, and that these rocks should be placed below the great unconformity 
which separates the Huronian from the Keewatin-Laurentian complex. 
They place the Hastings series of Eastern Ontario with the Huronian of 
Western Ontario.* 
The pre-Cambrian is being proved to be of more economic importance 
than it was formerly supposed to be. The great Sudbury and Cobalt ore 
deposits are found in these rocks, and promising indications of minerals 
of economic value are found widely extended over the area occupied by 
these rocks, which underlie at least one-half of the 3,756,000 square miles 
embraced in Canadian territory.” 
3. Report on the Erratic Blocks of the British Isles. 
See Reports, p. 169. 
4.An Outline of the Glacial Geology of Britain, illustrative of the 
Work of the Committee on Erratic Blocks. By A. R. Dwerry- 
House, D.Sc. 
5. The Glacial Phenomena of South Wales. 
By Avuprey Strawn, Sc.D., F.R.S. 
South Wales includes part of the southern margin of the glaciation 
of the British Isles. In the eastern part of the coalfield the drift has been 
transported southwards, nearly, but not quite, to the shore of the Bristol 
Channel. It contains great quantities of Old Red boulders from Brecknock, 
and it crossed the escarpments of lower Carboniferous rocks principally 
by way of the larger valleys. In the more central part of the coalfield the 
valleys trend south-westwards, and here also formed the channels by 
which Brecknock drift crossed the Carboniferous tract. The ice-sheet, 
however, was of sufficient magnitude to override all but the highest hills, 
to ignore sinuosities in the valleys, and to overflow from one valley into 
another. A part of the Pennant scarp, where it rises to a height of 
2,000 feet, formed locally an insuperable obstacle, but the distribution of 
boulders, and the strise prove that the Brecknock ice swept round it and 
reunited to the south of it. The drift of the central region rests upon 
a preglacial raised beach lying at about 15 to 20 feet above the present 
beach, and containing many shells of recent species. The western part 
of South Wales was occupied by ice which moved from north-west to 
south-east, and brought boulders from Pembrokeshire some miles up the 
Bristol Channel. This drift, which alone moved from sea landwards, is 
the only South Wales glacial deposit which contains shell-fragments among 
its boulders. It may be generally inferred that the continental shelf of 
which the British Isles form part should be considered in connection with 
the movements of the ice-sheets rather than the configuration of the land. 
That the shallow Irish Sea must have been occupied by ice is clear, not 
only near South Wales, but off the coast of North Wales. Too much 
importance also might easily be attributed to the Brecknock hills as a 
source of glaciation. Their effect, like that of the Pennant scarp referred 
to, may have been local. 
1 Geol. Soc. Am., 1907, and 17th Report, Bureau of Mines, Ontario. 
2 Journal Can. Mining Institute, 1909. 
