650 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1916. 



the same dimensions as the third lock, and was estimated to cost 

 $3,275,000. It will connect with the canal of the third lock. Work on 

 this fourth lock is also under way, the excavation for the lock pit 

 being about one-third done. 



The increased depth provided at the St. Marys Canal by the 

 new locks made it possible to use deeper-draft vessels. This con- 

 tinued until obstructions in the river channels in Lake Huron and 

 Detroit Elvers began to be felt. In 1902 a project was adopted to 

 provide for removing shoals in the entrance to the Hay Lake Chan- 

 nel, a part of Lake Huron, and for securing a new outlet channel 

 from Hay Lake by way of the old line through the West Neebish 

 Channel. This project is now completed, affording a double channel 

 from the Sault Locks to Lake Huron, having a clear depth of 21 

 feet. The expense of all this work has been $8,400,000. It is 

 worthy of note that the increase of depth and width in the old West 

 Neebish Channel was obtained by diverting the water from this 

 channel by cofferdams and then excavating the rock of the old river 

 bed " in the dry." This was the more economical m^ethod (pi. 1, fig. 

 2). The work took about 5 yeai's for completion and involved the 

 removal of 1,585,158 cubic yards of rock, at a cost of $1.36 per cubic 

 yard, and 5,461,120 cubic yards of earth, at a cost of $0.12f per 

 cubic yard, and 3,324,275 cubic yards of earth, at $0,129 per cubic 

 yard. These amounts are exclusive of " overdepths," for which half 

 these prices were paid. 



In the Detroit Eiver, also, there were obstructions at Limekiln 

 Crossing, which originally limited the draft of vessels to about 12^ 

 feet. As this river is on the route from the Lake Superior mines to 

 the ore ports on Lake Erie, the deepening of this obstruction was 

 needed as soon as the locks at St. Marys River admitted deeper- 

 draft vessels than could pass these obstructions. In 1874, a project 

 was adopted to provide for a channel from Detroit to Lake Erie 

 having a width of 300 feet and a depth of 20 feet. This project was 

 modified in 1888 to provide for a width of 440 feet. In 1902 a 

 greater depth was provided for, viz, 21 feet, and a greater width, 600 

 feet; and in 1910 a still greater depth of 22 feet was provided for. 

 This channel, known as the Amherstburg Channel, is now complete, 

 and cost $4,630,000. In 1907 a second channel was provided for, 

 known as the Livingston Channel, and was opened to navigation in 

 October, 1912, at a total cost of $6,734,000. This provides a separate 

 channel for up-and-down traffic in the Detroit Eiver. 



It will thus be seen that within a decade two new locks of great 

 capacity are being added to the others already constructed, making 

 four in all; and the channels at the upper and lower ends of Lake 

 Huron have been deepened and double lines for traffic provided, so 

 that up traffic may use a different line from that going down. 



