Note 14 — HOME STUDIES IN CHEMISTRY AND PHYSICS.
Reading edition
“Pneumatic Dispatch.” The packages are placed on easily rolling carriages which are nicely fitted within tubes. The force necessary to move them is produced by the alternate compression and expansion of air in large reservoirs. This compression and expansion is caused by forcing the water into, and then allowing it to run out of a connecting reservoir, the action being changed by a system of cocks.