London's Post Office Tube Line.

Fourteen years ago there was begun the construction of what is undoubtedly one of the most remarkable railways in the world. This is the Post Office tube line, which has been opened this year beneath the City of London, and which cost nearly a million and a half pounds sterling to build. Six and half miles in length, the railway runs right across the metropolis from east to west, linking up the Liverpool Street terminal of the L. and N.E. Railway with the G. W. Company's Paddington page 21 Station, and serving many post offices and sorting centres en route.

Between stations the tube is 9ft. in diameter, and it runs about 75 feet beneath the ground. It carries two tracks, each of 2ft gauge, and the stations consist of an island platform in two sections, between which are the control cabin and the lifts and conveying machinery for handling postal matter between the stations and the post offices above. The rolling stock consists of steel motor cars with an overall length of 4ft 11 1/4in, energised from a conductor rail. The cars may be operated singly or in trains of three cars. As a train leaves a station the section in the rear automatically becomes “dead,” and is made “alive” again on the train entering the next section but one in advance. In other words, there is always a “dead” section between successive trains. Illuminated diagrams in the control cabins reproduce the movements of trains on the tracks, and train speeds of up to 35 miles an hour are attained by these unique crewless trains of the new line.