The Cornwall Canal.—This canal, which is now being enlarged, between Moulinette and Milleroches, where several breaches have occurred in its banks, was originally constructed with a width of 100 feet at the bottom and 10 feet depth. The embankment was raised to 14 feet above the canal bottom, and was made 12 feet wide at the top with slopes on either side of two to one.
That portion of the canal embankment on the upper reach, which, for upwards of a mile in length (from Moulinette to Milleroches) holds the water in the canal at a level of about twenty feet above the branch of the St. Lawrence, which runs alongside, is in part founded upon the treacherous clay bottom in which were found springs of water, and in part in side cutting permeated by streaks of sand. The embankment over this ground was formed with extra care, the earth being laid on in courses with carts, and where the outer slope ran out into the river, it was protected by boulder stones along its outer edge. Where springs were found under the seat of the embankment they were led out to the river’s edge by French drains, and where the streaks of sand were encountered in the side cutting they were cut off by puddle trenches, 6 feet deep or more, and the bottom and side bank were lined with puddle, 3 feet thick, from the puddle trench to high-water mark. This mode of protection was not continuous over the whole line, but was confined to such parts of the bank only as appeared to require it.
Since the opening of the canal, there have been several breaches in this bank, the last and worst of all, which occurred in 1888, inflicting serious damage upon the trade of the St. Lawrence in that year.
The enlarged canal is to be 6 feet deeper than the old one. Sixteen feet of water, instead of 10 feet, implies greater strain upon the bank, and a deeper searching after the hidden springs and streaks of sand that may be interposed between the canal bottom and the river.
It has been proposed, with a view of avoiding this risk, to substitute a lake three miles in length for a canal where the breaks have occurred, and to throw dams across the narrow channels at the head and foot of Speek’s Island, in order to raise the water up to canal level.
The Sault St. Marie Canal.[122] —The Dominion of Canada, which borders on the Sault, has, or believes that she has, quite as great an interest in the development of the traffic on this route as her neighbours, and hence has resolved on constructing a canal at this point, which will, of course, be built on Canadian territory. So far back as 1852, the Canadian Government had surveys made with a view to the construction of a canal on the Canadian shore, and the execution of the project was recommended by the Canadian Canal Commission of 1871, but it was not until 1888 that the work was actually placed under contract.
On the Canadian side of the St. Mary’s river there is to be a lock of 18 feet, with a chamber 600 feet in length between the gates, 85 feet wide, and narrowed at the gates to 60 feet on opposite sides.
The Canadian Canal System generally.—A Commission appointed by the Dominion Government in 1870 to report on the best means of improving the canal system of Canada, adopted a series of recommendations, which have since been followed as far as possible. The principal of these were:—
Map showing the Position of the Sault St. Marie,
in relation to the American Lakes,
and the Trade from West to East.