that it filled all the Hudson River Valley, and covered the landscape for thousands of miles around them, riding over the tops of the Catskills and of the Adirondacks, and wearing them down and carrying fragments of rock torn from them hundreds of miles to the south and southwest,—­when I have told them all of this, I have usually given them a mouthful too big for them to masticate or swallow.  As a sort of abstract proposition contained in books, or heard in the classroom, they do not mind it, but as an actual fact, here in the light of common day on the hill above Slabsides, with the waters of the Hudson glistening below, and the trees rustling in the wind all about us, that is quite another matter.  It sounds like a dream or a fable.  Many of the processes that have made our globe what we see it have been so slow and on such a scale that they are quite beyond our horizon—­beyond the reach of our mental apprehension.  The mind has to approach them slowly and tentatively, and become familiar with the idea of them, before it can give any sort of rational assent to them.  It has taken the geologist a long time to work out and clear up and confirm this conception of the great continental glacier which in Pleistocene times covered so large a part of the northern hemisphere.  It is now as well established as any event in the remote past well can be.  In Alaska, and in the Swiss Alps, one may see the ice doing exactly what the Pleistocene ice-sheet did over this country.

II

The other day in passing a farmer’s house I saw where he had placed a huge, roundish boulder, nearly as high as a man’s head, by the roadside and had cut upon it his own name and date, and that of his father before him, and that of the first settler upon the farm, in the latter part of the eighteenth century.  It was an interesting monument.  I learned that the rock had been found in the bed of a small creek near by, and that the farmer had given a hundred dollars to have it moved to its place in front of his house.  Had I seen the old farmer I am sure I could have added to his interest and pride in his monument by telling him that it was Adiron-dack gneiss, and had been brought from that region on the back, or in the maw, of a glacier, many tens of thousands of years ago.  But it is highly probable that, were he an uneducated man, he would have treated my statement with contempt or incredulity.  Education does at least this for a man:  it opens his mind and makes him less skeptical about things not dreamed of in his philosophy.

This boulder had been rolled and worn in its long, slow ride till it was nearly round.  I have a much smaller boulder, probably from the same quarry, which I planted at the head of my garden for a seat when the hoe gets tired.  When it was dropped here on the land that is now my field, the bed and valley of the Hudson were occupied by the old glacier which, during its decline and recession, built up the terraces opposite me (where now stands a multimillionaire’s copy of an Italian palace), and which added to and uncovered the river slopes where now my own vineyards are planted.