The general character of the topography of the basins of the different lakes can be most readily understood from the standpoint of a physiographer by describing the region as an ancient belted coastal plain subsequently modified by glacial ice. The inner lowland, that bounded on the south and southwest by the Niagara cuesta, is occupied in part by the Georgian bay and in part by the bed of lake Ontario, there being also in Ontario an unsubmerged portion of this lowland lying between the two bodies of water just mentioned. The outer lowland, bounded by the margin of the Cumberland plateau, is in its lowest parts occupied (in part) by the beds of lakes Erie, Huron, and Michigan. The waters of Georgian bay, which is confluent with lake Huron, cover parts of the inner and innermost lowlands, and . . .