Democratic Sentinel, Volume 17, Number 9, Rensselaer, Jasper County, 17 March 1893 — PNEUMATIC TUBER. [ARTICLE]

PNEUMATIC TUBER.

’t'helr Extensive Use In liondon, Paris, Vienna and Berlin. In an article on “ Progress in Pneumatic Transmission,” in tne Engineering Magazine, William Allen Smith gives tho following facts regarding the use of pneumatic tubes in Europe. “ Pneumatic tubes for local transmission of telegrams are now used in all tho principal cities of Great Britain. At present about fifty miles of such tubes are in operation, requiring an aggregate of 400 horse power, and transmitting a daily overage of over 105,000 rhessages, or over 30,000,000 annually; more than half of these in London. The lengths of tubes vary greatly; the average length is about 630 yards; the greatest single length in London is 3,992 yards. The tubes are of lead, laid in cast-iron pipes, for protection, and are usually of two and onequarter inches inner diameter; some tubes of one and one-half and some of three inches inner diameter are used. As a general rule, with the same air pressure and diameter of tube, the speed varies inversely as the length of tube. In tubes not over a mile long the usual average speed is twenty-five to thirty miles an hour. The carriers are of gutta-percha, covered with felt, with a buffer at the front end, and an elastic band at the back or open end to hold in the messages. An ordinary carrier weighing two and threequarter ounces holds a dozen messages. The marked success of the British pneumatic service led to the adoption of similar systems in Paris, Vienna and Berlin. The pneumatic system of Paris was put into operation in 1866, and has grown steadily, so thut to-day in Paris tubes are used almost dxclusively for transmission of local telegrams and letters demanding quick delivery. A small stamped envelope, the petit bleu, costing 50 centimes, or 10 cents, is used for the message, which, dropped into a special post-box, is delivered anywhere in Paris within an hour, often in 25 minutes. In Vienna the “tube-post” was established in March, 1875. The nine districts of the city are connected with a central station. ' The “tube mail” is dropped into special post boxes, collected every half hour, forwarded to the central station and distributed. Pneumatic envelopes cost 15 kreutzers (about 6 cents), ordinary letters 3 kreutzers. “The letters” are delivered within one hour after mailing. The Vienna system consists of a main circuit of 5.34 miles, with three branch lines; total length, 7.2 miles.

In Berlin the Prussian postal authorities began in 1832 discussion of measures of rcilef for the overcrowded local telegraph system, and a pneumatic line was opened in 186) between the'Central Telegraph station and the Exchange building. The beginning of the present extensive “tube post” at Berlin dates from 1876, since which time it has been enlarged, until there are now over 28 miles of tube-line in the city with 38 stations. “Tube-letters” are to-day delivered in Berlin more quickly than telegrams at a cost equal to 7-i cents, and “tube postcards” at 6i cents. The tubes in Berlin arc of wrought iron, and have ail inner diameter of 6 > mm., equal to 2.55 inches. The system is operated by eight steam engines, aggregating only 128 horsepower. The British tube lines are laid on the radial system; that is, the different lines radiate from centres to the various branch stations to be reached. In Paris, Vienna, and originally in Berlin the various stations were connected by a series of polygons, around which the motion is uniformly in the same direction. A study of the two systems, for connection of a given number of stations under ordinary conditions, leads to the following comparative results: I. The polygonal system will require about 20 per cent, more tube length than the radial. 11. The polygonal system allows much greater use of compressed air for forwarding, as the passage around the polygons is always in the same direction. Rarefied air need be used only for the return passage in the links connecting the polygons, or for the return from a single, isolated station. In the radial system, rarefied air is used for half the passages. This shows greater economy in working for the polygonal system. 111. The time consumed in communicating between stations is less in the radial than in the polygonal system. In the latter, time is frequently lost by sending a message almost completely around the polygon.