Time and Change by John Burroughs — Read

He was a bold man who first conceived the idea of the great continental ice-sheet which in Pleistocene times covered most of the northern part of the continent, and played such a part in shaping the land as we know it. That bold man was Agassiz, who, however, was not bold enough to accept the theory of evolution as propounded by Darwin. The idea of the great glacier did not conflict with Agassiz's religious predilections, and the theory of evolution did. It was a bold generalization, this of the continental ice-sheet, one of the master-strokes of the scientific imagination. It was about the year 1840 that Agassiz, fresh from the glaciers of the Alps, went to Scotland looking for the tracks of the old glaciers, and he found them at once when he landed near Glasgow. We can all find them now on almost every walk we take to the fields and hills; but until our eyes are opened, how blind we are to them! We are like people who camp on the trail of an army and never suspect an army has passed, though the ruts made by their wagons and artillery and the ruins of their intrenchments are everywhere visible.

When I was a boy on the farm we never asked ourselves questions about the stones and rocks that encumbered the land -- whence they came, or what the agency was that brought them. The farmers believed the land was created just as we saw it -- stones, boulders, soil, gravel-pits, hills, mountains, and all -- and doubtless wished in their hearts that the Creator had not been so particular about the rocks and stones, or had made an exception in favor of their own fields. Rocks and stones were good for fences and foundations, and for various other uses, but they were a great hindrance to the cultivation of the soil. I once heard a farmer boast that he had very strong land -- it had to be strong to hold up such a crop of rocks and stones. When the Eastern farmer moved west into the prairie states, or south into the cotton-growing states, he probably never asked himself why the Creator had not cumbered the ground with rocks and stones in those sections, as he had in New York and New England.