In the United States, the first attempt to establish a pneumatic despatch system was made by Beach, about 1872,. who undertook the con struction of a tunnel six feet in diameter, under Broadway, New York City. His system was called the eatmospheric railway)) (q.v.) and contemplated the running of a car capable of seating 10 persons, through the tube, by the propelling energy of air pressure generated by a revolving fan. The project was abandoned after the completion of a small section of the tunnel. In 1904 the systems installed by the United States Post Department were as follows: The Philadelphia lines connecting the city post office with the Bourse, a distance of Z974 feet, and its extensions to the terminal stations of the Pennsylvania, and the Philadel and Reading railroads, a total distance of about one and one-half miles; and the New York City lines, connecting New York City post office with that of Brooklyn, and with the Grand Central Station and the intermediate postal sub-stations, a total distance of about 10 miles. The installation is on the plan of the Batcheller system, very similar to that employed by the English. Compressed air at pressures
ranging from 5 to 10 pounds per square inch is forced through wrought-iron tubes ranging from six to eight inches in diameter. They are laid in double lines so as to allow traffic in opposite directions, and are provided with au tomatic sending and receiving apparatus at all stations. In addition to the lines operated by the government, they are extensively used by private concerns in a great many cities, of which the systems operated by the Western Union Telegraph Company in New York City and Chicago are the most important. Since the perfection of automobile delivery trucks, city transportation has so improved that there is a tendency to discard pneumatic delivery for mail.
Bibliography.— More detailed information may be obtained from the following named pub lications: 'Pneumatic Tube Service) (published by the Postmaster-General, Washington); Batcheller, 'The Pneumatic Despatch S stem); Kemp, 'Year Book' (London 1902 ; and various publications on the subject by e Brit ish Postal Service.