Barges are now employed in the river for the purpose of ascertaining the depth of the water, and the nature of the bottom of the river. It is satisfactory to find that the rock on the Liverpool side, as the heading is advanced under the river, contains less and less water, and this the engineers are inclined to attribute to the thick bed of stiff bowlder clay which overlies the rock on this side, which acts as a kind of "overcoat" to the "under garments." The depth of the water in one part of the river is found to be about 72 ft.; in the middle about 90 ft.; and as there is an intermediate depth of rock of about 27 ft., the distance is upward of 100 ft. from the surface of low water to the top of the tunnel.
It is expected that the work will shortly be pushed forward at a much greater speed than has hitherto been the case, for in place of the miner's pick and shovel, which advanced at the rate of about ten yards per week, a machine known as the Beaumont boring machine will be brought into requisition in the course of a day or two, and it is expected to carry on the work at the rate of fifty yards per week, so that this year it may be possible to walk through the drainage heading from Liverpool to Birkenhead. The main tunnel works now in progress will probably be completed and trains running in the course of 18 months or two years.
The workmen are taken down the shaft by which the debris is hoisted, ten feet in diameter, and when the visitor arrives at the bottom he finds himself in quite a bright light, thanks to the Hammond electric light, worked by the Brush machine, which is now in use in the tunnel on both sides of the river. The depth of the pumping shaft is 170 feet, and the shaft communicates directly with the drainage heading. This circular heading now has been advanced about 737 yards. The heading is 7 feet in diameter, and the amount of it under the river is upward of 200 yards on each side. The main tunnel, which is 26 feet wide and 21 feet high, has also made considerable progress at both the Liverpool and Birkenhead ends. From the Liverpool side the tunnel now extends over 430 yards, and from the opposite shore about 590 yards. This includes the underground stations, each of which is 400 feet long, 51 feet wide, and 32 feet high. Although the main tunnel has not made quite the same progress between the shafts as the drainage heading, it is only about 100 yards behind it. When completed, the tunnel will be about a mile in length from shaft to shaft. In the course of the excavations which have been so far carried out, about 70 cubic yards of rock have been turned out for every yard forward.
Ten horses are employed on the Birkenhead side for drawing wagons loaded with debris to the shaft, which, on being hoisted, is tipped into the carts and taken for deposit to various places, some of which are about three miles distant. The tunnel is lined throughout with very solid brickwork, some of which is, 18 inches thick (composed of two layers of blue and two of red brick), and toward the river this brickwork is increased to a thickness of six rings of bricks--three blue and three red. A layer of Portland cement of considerable thickness also gives increased stability to the brick lining and other portions of the tunnel, and the whole of the flooring will be bricked. There are about 22 yards of brickwork in every yard forward. The work of excavation up to the present time has been done by blasting (tonite being employed for this purpose), and by the use of the pick and shovel. At every 45 ft. on alternate sides niches of 18 in. depth are placed for the safety of platelayers. The form of the tunnel is semicircular, the arch having a 13 ft. radius, the side walls a 25 ft. radius, and the base a 40 ft. radius.
Fortunately not a single life has up to the present time been lost in carrying out the exceedingly elaborate and gigantic work, and this immunity from accident is largely owing to the care and skill which are manifested by the heads of the various departments. The Mersey Tunnel scheme may now be looked upon as an accomplished work, and there is little doubt its value as a commercial medium will be speedily and fully appreciated upon completion.
DAM ACROSS THE OTTAWA RIVER AND NEW CANAL AT CARILLON QUE
By ANDREW BELL Resident Engineer
The natural navigation of the Ottawa River from the head of the Island of Montreal to Ottawa City--a distance of nearly a hundred miles--is interrupted between the villages of Carillon and Grenville which are thirteen miles apart by three rapids, known as the Carillon, Chûte à Blondeau, and Longue Sault Rapids, which are in that order from east to west. The Carillon Rapid is two miles long and has, or had, a fall of 10 feet the Chûte à Blondeau a quarter of a mile with a fall of 4 feet and the Longue Sault six miles and a fall of 46 feet. Between the Carillon and Chûte à Blondeau there is or was a slack water reach of three and a half miles, and between the latter and the foot of the Longue Sault a similar reach of one and a quarter miles.