Canadian Forestry Journal, February^ ipi6. 



379 



J. B. T. Photo. 



Burnt Timber on one of the branches of Severn River in the Interior Upland. 



by flat-lying Palaeozoic limestones, 

 but such rocks, whether granites or 

 limestones, are almost everywhere 

 buried beneath a thick deposit of 

 clay and sand representing the old 

 bottom of Hudson Bay when the 

 land stood four or five hundred feet 

 lower than it does at present. The 

 ancient sea bottom had been com- 

 posed of a very even floor of sand 

 and mud, and as it rose in compara- 

 tively recent times, geologically 

 speaking, it formed a vast and ap- 

 parently level plain, with old 

 beaches left as sand and gravel rid- 

 ges on it at various elevations, 

 formed during periods when there 

 were pauses in the process of land 

 elevation. The present shore of 

 Hudson Bay, on the margin of this 

 plain, is marked by a gravel beach 

 six to twelve feet high. From this 

 beach the land continues the same 

 gentle slope northward and east- 

 ward out beneath the tidal waters of 

 the Bay, so that at ebb tide it is 



possible to walk for long distances 

 along the tidal shore. 



A Gigantic Swamp. 



The Littoral plain has an average 

 slope towards the Bay of five feet to 

 the mile, and a width of about one 

 hundred miles, so that at its inner 

 border, where it joins the rougher 

 Interior Upland, it has an elevation 

 of from four hundred to five hund- 

 red feet above the sea. Several 

 large and many small streams flow 

 down this slope from the rock In- 

 terior Upland to the sea, and in their 

 courses have cut channels, some- 

 times a hundred or more feet in 

 depth, through the soft superficial 

 clays and sands, to the underlying 

 rock, but these channels have no- 

 where been widened to any consider- 

 able extent by lateral erosion, and 

 have not been converted into ma- 

 turely sloping valleys. This great 

 plain, with only two or three hills 

 breaking the monotony of its sur- 



