This light-house, known to mariners as the Cape Cod or Highland Light, is one of our "primary sea-coast lights," and is usually the first seen by those approaching the entrance of Massachusetts Bay from Europe. It is forty-three miles from Cape Ann Light, and forty-one from Boston Light. It stands about twenty rods from the edge of the bank, which is here formed of clay. I borrowed the plane and square, level and dividers, of a carpenter who was shingling a barn near by, and, using one of those shingles made of a mast, contrived a rude sort of quadrant, with pins for sights and pivots, and got the angle of elevation of the bank opposite the light-house, and with a couple of cod-lines the length of its slope, and so measured its height on the shingle. It rises one hundred and ten feet above its immediate base, or about one hundred and twenty-three feet above mean low water. Graham, who has carefully surveyed the extremity of the Cape, makes it one hundred and thirty feet. The mixed sand and clay lay at an angle of forty degrees with the horizon, where I measured it, but the clay is generally much steeper. No cow nor hen ever gets down it. half a mile farther south the bank is fifteen or twenty-five feet higher, and that appeared to be the highest land in North Truro. Even this vast clay-bank is fast wearing away. Small streams of water trickling down it at intervals of two or three rods have left the intermediate clay in the form of steep Gothic roofs fifty feet high or more, the ridges as sharp and rugged-looking as rocks and in one place the bank is curiously eaten out in the form of a large semicircular crater.
According to the light-house keeper, the Cape is wasting here on both sides, though most on the eastern. In some places it had lost many rods within the last year, and erelong the light-house must be moved. We calculated, from his data, how soon the Cape would be quite worn away at this point,—"for," said he, "I can remember sixty years back." We were even more surprised at this last announcement—that is, at the slow waste of life and energy in our informant, for we had taken him to be not more than forty—than at the rapid wasting of the Cape, and we thought that he stood a fair chance to outlive the former.
Between this October and June of the next year I found that the bank had lost about forty feet in one place opposite the light-house, and it was cracked more than forty feet farther from the edge at the last date, the shore being strewn with the recent rubbish. But I judged that generally it was not wearing away here at the rate of more than six feet annually. Any conclusions drawn from the observations of a few years or one generation only are likely to prove false, and the Cape may balk expectation by its durability. In some places even a wrecker's foot-path down the bank lasts several years. One old inhabitant told us that when the light-house was built, in 1798, it was calculated that it would stand forty-five years, allowing the bank to waste one length of fence each year, "but," said he, "there it is (or rather another near the same site, about twenty rods from the edge of the bank).
The sea is not gaining on the Cape everywhere: for one man told me of a vessel wrecked long ago on the north of Provincetown whose "bones" (this was his word) are still visible many rods within the present line of the beach, half buried in sand. Perchance they lie alone-side the timbers of a whale.