Pneumatic messaging system. Historical artwork of the intermediary station of a pneumatic capsule pipeline (PCP). The man is sending and receiving messages through the pipes at lower left and lower centre. Air from the storage tank (green) propels capsules containing the messages along the PCP. This technology has been used since the 19th century to transport mail, cash receipts, machine parts and numerous other products. The image is taken from the L'Illustration Journal Universel, 1873.