Hoosac Tunnel

a double-track railway tunnel through the Hoosac Mountain in northwestern Massachusetts. It is on the route from Boston to Troy. Its eastern entrance is 137 miles from Boston. The tunnel is nearly five miles long, the longest in the United States. It was seventeen years in building, and cost $13,000,000. The circulation is improved by a ventilation shaft near the middle. This shaft, over 1,000 feet in depth, acts like a tall chimney. See Tunnel