The first yearly report of the Bureau of Safety, I.C.C., on block signals to contain information as to the miles of road and miles of track on which alternating current track circuits were installed, was that issued as of January 1, 1914. Data taken from that report up to the last one issued is presented in the table below. Alternating Current Track Circuit Mileage ----------------+---------------+---------------- | Miles of Road | Miles of Track ----------------+---------------+---------------- January 1, 1914 | 3,289.2 | 4,144.6 January 1, 1915 | 2,728.2 | 5,814.9 January 1, 1916 | 3,186.7 | 6,679.0 January 1, 1917 | 3,336.2 | 6,823.6 January 1, 1918 | 3,748.0 | 7,530.1 January 1, 1919 | 4,496.6 | 8,620.2 January 1, 1920 | 4,676.5 | 9,026.0 January 1, 1921 | 4,786.1 | 9,120.2 ----------------+---------------+---------------- Alternating current track circuits have certain advantages over direct current track circuits, particularly in respect to their immunity to the dangerous effects of foreign direct current to which d.c. track circuits in some communities are subjected. The above table is therefore of interest as it shows the application of alternating current as made to Dr. Robinson's invention of the closed track circuit. Part IV THE TRACK CIRCUIT IN GREAT BRITAIN AND ON THE CONTINENT By T. S. Lascelles No satisfactory records appear to have been kept as to the origin and development of track circuiting outside the United States, which renders it very difficult to arrive at any conclusions that could serve as a basis for a real historical sketch upon this interesting subject. In view of the fact that the Signal Section of the American Railway Association proposes to publish a memorial to the late Dr. William Robinson, generally regarded as the inventor of the closed track circuit and certainly the first to utilize it in the control of an automatic block system, the following brief remarks may prove of interest to the writer's fellow members of the Signal Section. It is not suggested that they are in any sense complete, as to make a complete survey would require considerable investigation. They really represent the writer's present general understanding of the subject and are open to such criticism and correction as anyone may be able to offer to them, in England or elsewhere.