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A pneumatic tube system in Washington, D.C., in 1943. Pneumatic tubes (or capsule pipelines, also known as pneumatic tube transport or PTT) are systems that propel cylindrical containers through networks of tubes by compressed air or by partial vacuum. They are used for transporting solid objects, as opposed to conventional pipelines which ...
The air was compressed not by motorised means but by the pressure of 15 metres (49 ft) head of water held in reservoirs. A pressure of 2 standard atmospheres (200 kPa) was capable of being generated, which allowed a cylinder 5.5 inches (14 cm) long and carrying 40 messages to be transmitted in 60–80 seconds.
The consistently high costs of air mail curtailed this trend after the war. During the mid-1960s in response to the continuing increase of aircraft capacity, the UPU adopted the policy of maximizing air conveyance of mail and in the mid-1970s the concept of “surface air lifted” mail was developed in conjunction with the International Air ...
Airmail (or air mail) is a mail transport service branded and sold on the basis of at least one leg of its journey being by air. Airmail items typically arrive more quickly than surface mail , and usually cost more to send.
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In 1812, Medhurst wrote a book detailing his idea of transporting passengers and goods through airtight tubes using air propulsion. [154] Beach Pneumatic Transit was operated from 1870 to 1873 as a one-block-long prototype of an underground tube transport public transit system in New York City, following a concept by Alfred Ely Beach. The ...
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