The Grenville Canal (around the Longue Sault) with seven locks, and the Chûte à Blondeau with one lock, are fed directly from Ottawa. But with the Carillon that method was not followed as the nature of the banks there would have in doing so, entailed an immense amount of rock excavation--a serious matter in those days. The difficulty was overcome by locking up at the upper or western end 13 feet and down 23 at lower end, supplying the summit by a 'feeder from a small stream called the North River, which empties into the Ottawa three or four miles below Carillon, but is close to the main river opposite the canal. In 1870-71 the Government of Canada determined to enlarge these canals to admit of the passage of boats requiring locks 200 feet long, 45 feet wide, and not less than 9 feet of water on the sills at the lowest water. In the case of the Grenville Canal this was and is being done by widening and deepening the old channel and building new locks along side of the old ones. But to do that with the Carillon was found to be inexpedient. The rapidly increasing traffic required more water than the North River could supply in any case, and the clearing up of the country to the north had materially reduced its waters in summer and fall, when most needed. To deepen the old canal so as to enable it to take its supply from the Ottawa would have caused the excavation of at least 1,250,000 cubic yards of rock, besides necessitating the enlargement of the Chûte à Blondeau also. It was therefore decided to adopt a modification of the plan proposed by Mr. T.C. Clarke, of the present firm of Clarke Reeves & Co, several years before when he made the preliminary surveys for the then proposed "Ottawa Ship Canal," namely to build a dam across the river in the Carillon Rapid but of a sufficient height to drown out the Chûte à Blondeau, and also to give the required depth of water there.