ST. CLAIR RIVER RAILWAY TUNNEL. Some months ago we published a cable message reporting the opening, with appro- priate international ceremonies, of the St. Clair river railway tunnel, one of the greatest engineering triumphs of the age. We condense the following particulars of this great work from the Toronto Globe of September 19 :- The tunnel runs from Sarnia, Ontario, to Port Huron, Mich., and will be used by the traffic of various roads, including ihe Grand Trunk of Canada and its leased lines, the Great Western, the Chicago and Grand Trunk, the Port Huron and Detroit, the Detroit, Grand Haven and Milwaukee, the Michigan Air Line, the Toledo, Saginaw, and Muskegon, the Cincinnatti, Saginaw and Mackinac, etc. These railways have hitherto been connected by an enormous steam ferry service between Point Edward and Point Graliot, a few miles from Sarina and Port Huron respectively. The commerce on the St. Clair river is said to exceed that of any other stream in the world, and the marine interests were united against the construction of any kind of bridge. The more feasible plan appeared to be a tunnel. Yet this, too, presented almost insuperable difficulties, contractors who would travel anywhere through dry land or rock drawing the line at quicksand and clay under water. The three men most responsible for the suc- cessful solution of the problem are Sir Henry W. Tyler. president of the Grand Trunk railway, Sir Joseph Hickson, late general manager, and Mr Joseph Robson, of Hamilton, chief engineer. Sir Joseph Hickson became general manager of the road in 1874, the Grand Trunk having reached Sarnia in 1858. Mr. Hickson (he was not a knight in those days) foresaw the enormous advantages that would accrue to his road from rapid transit at the St. Clair river, and immediately set to work to secure it. The event of to-day shows the success of his efforts. In 1884 Messrs. Hobsen an Hillman selected a site and made trial borings in the rock to a depth of 86ft below the level of the water, the river's greatest depth being 40.47ft, and its width about a mile. The strata were found to be as follows :-About 2ft of common yellow sand, like that of the sea-shore ; about 12ft of a mixture of quicksand and blue clay; next, down to the rock, about 21ft of blue clay, adhesive and putty-like, and increas- ing in tenacity as it increased in depth. Drawings and plans were made, and a com- pany for the construction of the tunnel was organised in 1886. Mr. Hickson was president and Mr. Hobson chief engineer. After various tests and experiments, ren- dered neceseary by the difficult nature of the soil to be dealt with, the great excavating shields were started, one on each side of the river. The American shield was started on Thursday, July 11, 1889, and the Canadian on September 21 of the same year. They met edge to edge at 11.30 p.m. Saturday, August 30, 1890, after travelling 6000ft. The shields' shells remain there. The American shield had done most, but it started first. The work had been pushed day and night, in three shifts, each of eight hours. Each shield averaged an advance of 10ft per day, and the most accomplished in any one day was 27ft 10in. The easiest progress was towards the Canadian side. The excavating shield,which was in- vented by Mr A. L. Beach, of New York, is a strong cylinder resembling a big barrel with both heads out. The walls of the tunnel are built up inside this cylinder, and then by means of an immense pressure, exerted by hydraulic jacks, the shield is drawn partly off and forced farther ahead into the soill yet to be pierced. Each of the shields weighed 80 tons, and they were manufactured in Hamilton. The observa- tion of the direction of the shield was very interesting. From a small house in the line of the tunnel these observations were taken every morning. The transit was a fine one, made especially in London, and was set on masonry. A series of disks and a tube with cross wires enabled the engineer to discover, to the smallest fraction of an inch, any deviation in the direction of the shield. This devia- tion was marked on a diagram. One copy was sent to Chief Engineer Hobson at Hamilton and one was left at the works. The man in charge of the hydraulic rams was informed of any variation in the shield and he adjusted the jacks to correct any error. This deviation was rarely more than a quarter of an inch. When the shields met they were exactly in line, which was a triumph for the engineers. When the tunnel from the Canadian side reached the bed of the river quicksand and water caused much trouble, and for a while it was feared the entire enterprise would have to be abandoned. A remedy was found at last in compressed air. At the line of the river on both sides airtight bulkheads of brick and cement were built across the tunnel. Each side of these bulk heads had two air chambers 7ft in diameter and 17ft long, with air tight doors at each end. One of these air chambers was built over each car track. The work in the section next the shield was begun under an air pressure of ten pounds to the square inch, which was gradually increased from time to time until the men worked under an artificial pressure of 22 pounds per square inch, or a total atmospheric pressure of 37 pounds per square inch. Quicksand caused the highest air pressure to be exerted on the Canadian side. The air pressure kept the clay and quicksand and water from rushing in at the front of the shield and endangering the lives of the workmen. On Sunday afternoon, August 24, 1890, the two gangs of workmen talked and passed articles through the anger hole between the two shields, and shortly after- wards the earth was removed. There was still, however, much work to be done. The tunnel was very dirty. It had to be cleaned, and was then covered with a preparation to prevent its rusting. The tramway's bed of clay was removed, the brickwork was plastered over, safety plat- forms and ladders were erected, and various other such details attended to. Much work also remained to be done on the approaches. The actual length of the tunnel itself under the river is 6026ft and with its ap- preaches 11,553. The average number of men employed was 100. They were un- usually intelligent and took great personal interest in the success of the undertaking. The total cost of construction of the tunnel Sproper was 1,460,000dols. Goon Morning ! Have you used Pear's soap ? Pear's soap for toilet and nursery, especialy prepared for the delicate skin of ladies and children, and others sensitive to the weather, winter and summer. Scented tablets 1s each ; smaller (unscented) 6d.