There was much early enthusiasm for pneumatic propulsion, and some lines were built. London had a working system, the London Pneumatic Dispatch Railway, 1865.[1] It could carry passengers, but was really for mailbags. Unfortunately, the elevator hadn&#x27;t been invented yet, and getting the mailbags up from track level to post office level quickly was a bottleneck.  Also, the system leaked air at many points.  (Good rubber gaskets are quite modern - oil resistant rubber (Neoprene) dates from WWII. Early systems used oiled leather.  There were many early pneumatic and steam powered ideas that didn&#x27;t work because gaskets and piston rings weren&#x27;t good enough yet.)<p>[1] <a href="http:&#x2F;&#x2F;www.londonreconnections.com&#x2F;2015&#x2F;londons-lost-pneumatic-railway-the-worlds-2nd-oldest-underground&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.londonreconnections.com&#x2F;2015&#x2F;londons-lost-pneumat...</a>