Pneumatique

:: Paris, image source
Pneumatic post or pneumatic mail is a system to deliver letters through pressurized air tubes. It was invented by the Scottish engineer William Murdoch in the 1800s and was later developed by the London Pneumatic Dispatch Company. Pneumatic post systems were used in several large cities starting in the second half of the 19th century (including an 1866 London system powerful and large enough to transport humans during trial runs - though not intended for the purpose), but were largely abandoned during the 20th century.Recently I came across this interesting text on the pneumatic post in Paris. A major network of tubes was in use until 1984, when it was finally abandoned in favor of computers and fax machines. This invisible network under the city is highly fascinating in terms of its size and capacity. For example in Paris the peak was in 1945 where 11.271.228 deliveries were sent through the 467 km long tube system. :: Rohpost Berlin 1885, image source
:: Damages on Berlin's pneumatic post after WW II, image source
Also Berlin sustained a pneumatic system called 'Rohrpost' of 400 km until the years 1963 (West) and 1976(East).:: Prague, image source
In Prague, in the Czech Republic, a network of tubes extending approximately 60 kilometres in length still exists for delivering mail and parcels. Following the 2002 European floods, the Prague system sustained damage, and operation was mothballed indefinitely.:: New York City's pneumatic subway in 1870, image source
New York City even had a pneumatic subway in the 1870s. Over 400,000 New Yorkers took a joy ride underground during the three years the pneumatic subway was open for demonstration. In 1873 , a stock market crashed killed financial support and thus the extension of the pneumatic subway.