How observation may lead to a bold and successful experiment is told by Mr. L. E. Chittenden, Register of the Treasury under President Lincoln, in his Personal Reminiscences:-- A Lesson from a Bank-Swallow. Between the Winooski Valley and Lake Champlain, north of the city of Burlington, lies a broad sand plain high above the lake level, through which the Central Vermont Railroad was to be carried in a tunnel. But the sand was destitute of moisture or cohesiveness, and the engineers, after expending a large sum of money, decided that the tunnel could not be constructed because there were no means of sustaining the material during the building of the masonry. The removal of so large a quantity of material from a cut of such dimensions also involved an expense that was prohibitory. The route was consequently given up and the road built in a crooked ravine through the centre of the city, involving ascending and descending grades of more than 130 feet to the mile. When the railroad was opened these grades were found to involve a cost which practically drove the through freights to a competing railroad. There was at the time a young man in the engineers’ office of the railroad who said that he could tunnel the sand bank at a very small cost. He was summoned before the managers and questioned. “Yes,” he said, “I can build the tunnel for so many dollars per running foot, but I cannot expect you to act upon my opinion when so many American and European engineers have declared the project impracticable.” The managers knew that the first fifty feet of the tunnel involved all the difficulties. They offered him, and he accepted, a contract to build fifty feet of the structure. His plan was simplicity itself. On a vertical face of the bank he marked the line of an arch larger than the tunnel. On this line he drove into the bank sharpened timbers, twelve feet long, three by four inches square. Then he removed six feet of the material and drove in another arch, just inside the first one, of twelve-foot timbers, took out six feet more of sand, and repeated this process until he had space enough to commence the masonry. As fast as this was completed the space above it was filled, leaving the timbers in place. Thus he progressed, keeping the masonry well up to the excavation, until he had pierced the bank with the cheapest tunnel ever constructed, which has carried the traffic of a great railroad for thirty years, and now stands as firm as on its completion.