The speed of the trains of carriers in the Paris tubes is from fifteen to twenty-three miles per hour, and the average time that elapses from the receipt of a message until its delivery is from forty to forty-five minutes.
The Pneumatic Telegraph of other Cities.
—A system similar to the one just described is used in Vienna. It differs some in details of apparatus, but the carriers are despatched around circuits in trains, stopping at each station, where some carriers are removed and others inserted. Brussels also is not without its system of pneumatic tubes for the transmission of telegrams.
Pneumatic Tubes in America.
—Turning our attention now to our own country, we cannot pass without mention some experiments of Alfred E. Beach with pneumatic railways, made nearly thirty years ago. His first experiment upon a large scale was made at the American Institute Fair held in New York City in 1867. Here he had constructed a circular wooden tube, one hundred and seven feet long and six feet in diameter. A car that would seat ten people ran upon a track laid down inside the tube, and was propelled by a helix fan ten feet in diameter, making two hundred revolutions per minute. He next tried his railway upon a practical scale, constructing an eight-foot tunnel for two hundred feet under Broadway, starting at the corner of Warren Street. A car was propelled by a large rotary blower located in the basement of a building near by. The blower was kept constantly running, and the car was sent alternately in one direction and then the other by changing valves at the blower. Few people know that this experimental line still exists under Broadway as Mr. Beach left it.
The most extensive use of small pneumatic tubes in this country has been in our large retail department stores for despatching cash to and from a centrally located cashier’s desk. Seamless brass tubes are usually used, and, since the tubes are short, the air is either compressed or exhausted by means of positive rotary blowers. At the outlying stations the tubes are usually open to the atmosphere, while at the central station simple forms of valves are used for sending and receiving. An outgoing and a return tube are always used, and the air is kept in constant circulation. The carriers are of metal with felt packing rings and open on the side. These cash-carrying systems have come into use during the past twenty-five years.
The Western Union Telegraph Company uses small tubes to transmit its messages to a considerable extent in some of our large cities. In 1876 four lines were laid in New York City from the main office on Broadway: two to the branch office at No. 14 Broad Street, one to 134 Pearl Street, and one to the Cotton Exchange. Since then this company has laid a double line about two miles in length under Broadway to its up-town office. It also uses tubes to send messages from the receiving desks to the operating rooms within the buildings.
Many of our large hotels use pneumatic tubes to transmit messages to the different floors and offices of the buildings, taking the place of messenger, or bell boys, who formerly did this service.
We call especial attention to the fact that in all the systems that we have mentioned which are in use both in this country and in Europe, none of the tubes are larger than three inches internal diameter; also that in all the systems, except in Paris where the carriers are despatched in trains, the carriers are so light and move so slowly that they can be stopped by allowing them to come in contact with some solid object, such as a box into which the carriers drop. Very few of the tubes are more than two miles in length, and most of them are less than one mile. A speed of more than thirty miles per hour has seldom been attempted, and usually it is much less than this.