Southwest of Hudson Bay and James Bay is a great lowland region occupied by nearly flat lower Paleozoic rocks and, in the extreme southern part, by an area of Lower Cretaceous formations. This belt of sediments is about 800 miles long and varies in width from 75 to 225 miles. It extends northwest from Latitude 50° 00′ to about Churchill at 59° 00′. Seventy-five per cent of the area lies within the province of Ontario; the remaining 25 per cent is in the northeast corner of Manitoba. The total area of this great coastal plain is about 125,000 square miles.

“Hudson Bay” and “James Bay” have always sounded very remote even to the native Canadian. To-day, however, this region lies well within the frontiers of mining explorations which are now being carried out in the Ungava and Great Bear lake districts, lying east and west of James Bay and 400–800 miles farther north. Even though the area of greatest interest is nowhere more than 200 miles from the railway, it is practically unexplored both geologically and topographically excepting in a reconnaissance fashion.

Throughout the lowland area, the bedrock is covered by a thick mantle of marine and glacial deposits of Pleistocene age so that outcrops are exposed only at low water level on some of the main streams.

The Paleozoic sediments are chiefly marine in origin and are composed largely of limestone and shale with small amounts of gypsum and sandstone. Ordovician, Silurian, and Devonian strata are each known to