The chamber is filled and emptied by culverts of large dimensions, under the mitre sills, without producing any disturbance of the vessel, because the tunnel or culvert runs the whole length of the chamber, with openings at the top, which are so arranged as to distribute the force of the inflowing current along the centre, entirely under the vessel’s keel. In 1886, when the Canadian and Pacific Railway steamer _Arthabaska_ passed through the lock, it took one minute and a half to close the upper gates, seven minutes and a half to empty the lock, and one minute and a half to open the lower gates. Altogether, from the time of entering the lock to the time of going out of it again, the passage was made in thirteen minutes, and there was no hurry about it. It is only by the great initial pressure afforded by the accumulator, about 600 lbs. to the square inch, that the valves and gates could be commanded with so much ease and rapidity. This system has been seven years in operation, and its efficiency proves the great care and skill with which all the details of construction have been worked out. The lock was six years in building, and cost, including the enlargement of the canal, about three millions of dollars. The two other locks, now called the “old locks,” built by the State of Michigan, and first opened in 1855, are still in use. These old locks are combined, having lifts of 9 feet each to overcome the whole fall of 18 feet. The gates are suspended from pillars seated on the coping of the quoins, and the chambers are filled and emptied through the gates in the old-fashioned way. The old canals and locks were assumed by the United States Government in 1881. The shipping that goes through this canal all passes free, both domestic and foreign. The staple articles of the commerce using the canal are coal, copper, flour, grain, iron ore, pig and manufactured iron, lumber, salt, silver ore, and building stones. Before the opening of the canal the commerce here was nil. It now threatens soon to exceed the capacity of both locks, in view of which the United States Government has already commenced a second enlargement, the estimated cost of which is nearly five millions of dollars. This new lock is to occupy the site of the old combined locks, and is to surpass all other locks in the grandeur of its dimensions. It will have a chamber 800 feet long between the gates, the width, both in the chamber and at the gates, will be 100 feet throughout, and the depth on the sills will be 21 feet. Of course there are no vessels on the upper lakes large enough to fill such a lock as this, but it is designed to pass a fleet through at a single lockage, including tug-boats, with their flotilla of barges. The canal is to be uniformly 20 feet in depth.