The length of tunnel beneath the water is 2,290 feet, while that under dry land represents another 3,748 feet, making a total length of 6,932 feet. To this must be added 5,580 feet of approaches, which brings the total extent of the work to nearly 12,000 feet, or 2¼ miles. It cost £540,000, or $2,700,000, and has always ranked as a noteworthy achievement in this particular branch of engineering. Owing to the steepness of the approaches on either side special locomotives had to be built to handle the traffic through this artery. They were powerful creations of the railway engine designer, and when they appeared were the largest steam locomotives in the world. They could haul a train weighing 760 tons, though at times the pace was slow. But traffic between the United States and Canada increased by leaps and bounds, owing to the provision of this tunnel, with the result that in a very few years the railway authorities found that the tube was quite overtaxed. A solemn conclave was held as to the best ways and means of meeting this development. The track could not be doubled; so the question was how to increase the existing hauling capacity of a single engine. Steam could not meet the question, so was ruled out of court. Then an engineer suggested electrification, and advanced a report to show how the weight of each train might be increased by nearly 25 per cent. with quicker working, and consequently would facilitate the passage of a greater number of trains in a given time. This engineer, Mr. Bion Arnold, was authorised to proceed with his scheme and to complete his plans for the electrification of the tunnel. He did so, and as a result a specification was drawn up requiring the haulage of a train weighing 1000 tons over the 2¼ miles in 15 minutes, with a maximum speed of 25 miles and a minimum speed of 10 miles per hour respectively. When the plans were made known it was realised that the project comprised the most ambitious electrical undertaking that ever had been attempted up to that time in railway operations, especially as it was insisted that the electrical system should be of a type which constituted its first application to heavy steam railway working. This is what is known as the single-phase alternating current system with overhead conductor.