The head of Lake Superior is 1400 miles from New York. Of this distance some 880 miles are deep water navigation by the Lakes, the outlet of which is St. Mary’s River. The St. Mary’s Strait is 75 miles long, and in this distance there is a fall of 20 feet 4 inches, of which 18 feet 2 inches occur at the Sault, while the remainder of the descent, 2 feet 2 inches, is distributed over the first 35 miles below that point. Hence the river is tortuous, and navigation is rendered unsafe by the rapids, although from a point 50 miles below the foot of Lake Superior navigation is good for the remainder of the distance of 25 miles to Lake Huron. In 1855 the St. Mary Falls Canal was built for the purpose of overcoming the fall between the Lakes Superior and Huron. The length of the canal is only about one mile, so that, as compared with the Suez and other ship canals, its extent is unimportant. But so far as its traffic is concerned, this is the most important canal in the world. Commencing with an annual tonnage of only about 100,000 tons at the time of its construction, the canal now disposes of an annual tonnage of over six millions, thus exceeding the tonnage passed over the Suez Canal by nearly a million of tons. In 1855, two locks were built on the St. Mary’s Falls Canal, each 70 feet wide and 350 feet long between the gates. These locks could not accommodate vessels drawing more than 11½ feet. But in 1880, when the canal had been transferred by the State of Michigan to the United States, as a work of national importance, the Government undertook the construction of a new lock, which was opened in 1881, and which has been described by competent engineers as the finest piece of hydraulic engineering on the American continent. The lock is at the lower end, and is 515 feet long between the gates and 80 feet wide in the chamber, with 17 feet of water on the sills. The lift is 18 feet, more or less, according to the fall in the rapids between Lake Superior and Lake Huron. The gates are not set opposite to each other on the same axis, but on parallel axes 20 feet apart, so that the width between the gates is reduced to 60 feet, while in the chamber it is 80 feet, the difference being met by reverse curves on either side. Advantage is taken of the natural water power created by the lock to establish by the side of it an accumulator for operating the gates and valves by hydraulic pressure—in the same manner as at the London and Liverpool docks—which works admirably.