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Dead medium: Pneumatic mail (Part Two)
From: (Dan Howland)
Source(s): Scientific American, December 11, 1897 "In 1865, Seimens & Halske, of Berlin, laid down in that city a system of pneumatic tubes for the transmission of telegraph messages. The wrought iron tubes, 2 1/2 inches in diameter, were in duplicate, one being used for transmitting and the other for receiving messages. They ran from the telegraph station to the Exchange, a distance of 5,670 feet. The tubes were looped together at the Exchange and a continuous flow of air was maintained by a compressor at one end and an exhauster at the other.

"The modified system now in use is worked by means of large storage tanks, containing either compressed or rarefied air, and it comprises 38 stations and more than 28 miles of tubing 2.55 inches in diameter.

"The pneumatic tube system in Paris dates from the same year as that of Berlin. Here a novel feature was introduced in the method of compressing the air, for instead of using a steam engine it was compressed in the tanks by displacement with water from the city mains. The tubes of the present system are 2.55 inches diameter, and the carriers are made up in trains of from 6 to 10, with a leather-covered piston at the rear which fits the tubes snugly and drives them forward. The tubes are wrought iron and the speed is 15 to 23 miles an hour."

Dan Howland (