The stream, as it approaches the arch of the Bridge, is deep and of a dark green color. The chasm, from the top of the ledge, is about sixty feet deep, and the ravine three hundred feet in length. Geologists say that the ravine was formerly spanned by two ledges of rock, one of which is now in ruins. The piles of rocks in the chasm south of the southern portal of the arch are dazzling white, seen in the noonday sunshine. The fall of water, in its descent through the ravine, is about forty feet to the three hundred feet, so that the eddies play and whirl rapidly through the irregular bed. A wooden tile, or raceway, was hung high over the chasm, across a leaning crag of the original ledge,—conveying water power thereby to mills below. This old structure leaked, and as I descended the banks below, I saw some of the most gorgeous miniature rainbows spanning the depths, as the sunshine fell upon the mist near the arch. A lad once made a wager with his comrades that he could cross over the ravine upon this wooden tile. The old weather-worn log was slippery with mould and mosses. In making his daring and perilous trip, the youth lost his footing, and fell headlong into the heart of the chasm. Following the fall, a terrific thunderstorm passed through the Hoosac, and night closed over the chasm. The next morning the boy’s lifeless body was recovered. The wooden structure is now replaced with an iron tiling. I passed on down the path on the west bank, until I reached an immense marble boulder, which was draped with dainty ferns and mosses. Little rivulets flowed from its sides, and climbing around to its southern brow, I was delighted to find many luxuriant plants of Walking Ferns—this making the fifth excursion in succession in which I had found this rare plant. I entered the ravine below the boulder, and picked my way up the chasm to the southern portal of the arch, where I became wet through from the mist above, as I ventured to look through the cave. Returning, I found a path up the east bank leading to Marble Quarry and the mill below, where grave-stones, door-stones, and various ornaments are manufactured. The most useful piece of work ever turned out here was, in my mind, the Williams College sun-dial tablet, which Hawthorne observed in 1838 as being as large as the top of a hogshead.[59] I have later discovered that this dial was placed near that old Astronomical Observatory on Consumption Hill, near the present College Library,—the first building of its kind erected in the United States, for the study of the worlds above, by Professor Albert Hopkins, in 1838. The bronze sun-dial was supported upon the marble table which Hawthorne saw at the quarry. Around it was carved in the soft marble the now dim inscription: “HOW IS IT THAT YE DO NOT DISCERN THIS TIME.” This dial is now among the relics in the College Museum.