The present paper is offered as a contribution to the already voluminous literature on the origin of the basins of the Great lakes in the belief that the matter here presented not only is of great importance in the attempt to find a correct solution of the problem, but also because, so far as the writer’s study of the literature has gone, the facts here set forth have been largely overlooked in the earlier studies of this question. In a paper published three years ago the writer very briefly outlined some of the facts and conclusions given here in more detail.* The important bearing which the studies then made appeared to have on the origin of the Saint Lawrence outlet from lake Ontario led him to delay fuller publication until he had been able to continue and extend the field work begun at that time. During the past two . . .