Some additional data gathered in recent field-work seem to afford a clear explanation of the drainage history of this region, about certain features of which divergent views have previously been held, and also have a bearing on the more general problems of the Pleistocene history of the Hudson-Champlain Valley. The key to the drainage problems involved is found in the repeated shifting of the course of the Iroquois-Mohawk River as its flooded and sediment-bearing waters flowed across an area from which the static waters of the Mohawk-Hudson region (here referred to as Glacial Lake Albany) were receding. The origin and distribution of the sand-plains of the region, the origin of Saratoga Lake and of Round Lake, of the “old channel of the Hudson west of Schuylerville,” and of the Coveville Inlet of the Hudson River are explained. The features discussed are within the areas covered by the Schenectady, Saratoga, . . .