Image Description from historic lecture booklet: "When the glacier had melted off in the vicinity of the present Chicago and Detroit two points north of the divide, the eastern region about the Mohawk and St. Lawrence valleys, was still full of ice. It will readily be seen, therefore, that there were lakes gathered on the north. As the ice melted farther back these lakes became greater in size and often changed much in form. But in time the ice melted out of the Mohawk Valley in New York and the drainage of these glacial Great Lakes poured out between the Adirondacks and Catskills to the Hudson and the sea. Still later, the glacier melted out of the St. Lawrence Valley, and the Great Lakes came to their present levels and forms.
Image Description from historic lecture booklet: "This kind of plain was made by the streams that came from beneath the ice as they wandered this way and that and dropped their load. Many such plains are found in the Northern states, and the process of their making may be witnessed at the margins of many glaciers of Alaska."
Image Description from historic lecture booklet: "Every large snow-field is also an ice-field, for where snow accumulates to great depth and lies long upon the surface, it is changed to ice. the beginning of this change may be seen in the snow a few days after it falls, for it soon loses its light, flaky character and becomes granular, so that it feels harsh to the hand. The change is very distinct in the last banks of snow in the spring. They are made up of coarse grains (granules) of ice, sometimes as larges as peas. The change from flakes of snow to granules of ice is due, in part, to the melting of the snow and the freezing of the water. If there is much snow, it is compressed by its own weight, and after being compacted in this way, the freezing of the sinking water binds the granules together. By this and perhaps other process, the large part of every thick snow-field becomes an ice-field merely coated over with snow."