[CHAPTER XXII]
PNEUMATIC MAIL TUBES
You put your money on the counter. The shop assistant makes out a bill; and you wonder what he will do with it next. These large stores know nothing of an open till. Yet there are no cashiers' desks visible; nor any overhead wires to whisk a carrier off to some corner where a young lady, enthroned in a box, controls all the pecuniary affairs of that department.
While you are wondering the assistant has wrapped the coin in the bill and put the two into a dumb-bell-shaped carrier, which he drops into a hole. A few seconds later, flop! and the carrier has returned into a basket under another opening. There is something so mysterious about the operation that you ask questions, and it is explained to you that there are pneumatic tubes running from every counter in the building to a central pay-desk on the first or second floor; and that an engine somewhere in the basement is hard at work all day compressing air to shoot the carriers through their tubes.
Certainly a great improvement on those croquet-ball receptacles which progressed with a deliberation maddening to anyone in a hurry along a wooden suspended railway! Now, imagine tubes of this sort, only of much larger diameter, in some cases, passing for miles under the streets and houses, and you will have an idea of what the Pneumatic Mail Despatch means: the cash and bill being replaced by letters, telegrams, and possibly small parcels.
"Swift as the wind" is a phrase often in our mouths, when we wish to emphasise the celerity of an individual, an animal, or a machine in getting from one spot of the earth's surface to another. Mercury, the messenger of uncertain-tempered Jove, was pictured with wings on his feet to convey, symbolically, the same notion of speed. The modern human messenger is so poor a counterpart of the god, and his feet are so far from being winged, that for certain purposes we have fallen back on elemental air-currents, not unrestrained like the breezes, but confined to the narrow and certain paths of the metal tube.
The pneumatic despatch, which at the present day is by no means universal, has been tried in various forms for several decades. Its first public installation dates from 1853, when a tube three inches in diameter and 220 yards long was laid in London to connect the International Telegraph Company with the Stock Exchange. A vacuum was created artificially in front of the carrier, which the ordinary pressure of the atmosphere forced through the tube. Soon after this the post-office authorities took the matter up, as the pneumatic system promised to be useful for the transmission of letters; but refused to face the initial expense of laying the tube lines.
When, in 1858, Mr. C. F. Varley introduced the high pressure method, pneumatic despatch received an impetus comparable to that given to the steam-engine by the employment of high-pressure steam. It was now possible to use a double line of tubes economically, the air compressed for sending the carriers through the one line being pumped out of a chamber which sucked them back through the other. Tubes for postal work were soon installed in many large towns in Great Britain, Europe, and the United States; including the thirty-inch pneumatic railway between the North-Western District post office in Eversholt Street and Euston Station, which for some months of 1863 transported the mails between these two points. The air was exhausted in front of the carriage by a large fan. Encouraged by its success, the company built a much larger tube, nearly 4 1 / 2 feet in diameter, to connect Euston Station with the General Post Office. This carried fourteen tons of post-office matter from one end to the other in a quarter of an hour. There was an intermediate station in Holborn, where the engines for exhausting had been installed. But owing to the difficulty of preventing air leakage round the carriages the undertaking proved a commercial failure, and for years the very route of this pneumatic railway could not be found; so quickly are "failures" forgotten!
The more useful small tube grew most vigorously in America and France. In, or about, the year 1875 the Western Union Telegraph Company laid tubes in New York to despatch telegrams from one part of the city to the other, because they found it quicker to send them this way than over the wires. Eighteen years later fifteen miles of tubes were installed in Chicago to connect the main offices of the same company with the newspaper offices in the town, and with various important public buildings. Messages which formerly took an hour or more in delivery are now flipped from end to end in a few seconds.
The Philadelphia people meanwhile had been busy with a double line of six-inch tubes, 3,000 feet long, laid by Mr. B. C. Batcheller between the Bourse and the General Post Office, for the carriage of mails. The first thing to pass through was a Bible wrapped in the "Stars and Stripes." A 30 horse-power engine is kept busy exhausting and compressing the air needed for the service, which amounts to about 800 cubic feet per minute. Philadelphia can also boast an eight-inch service, connecting the General Post Office with the Union Railway Station, a mile away. One and a half minutes suffice for the transit of the large carriers packed tightly with letters and circulars, nearly half a million of which are handled by these tubes daily.