At any subway station, a gust of wind announces the arrival of a train long before it can be seen or heard. Like a piston, the train pushes the air in front of it – but could air be used to push the train?
Such “pneumatic railways” promised a smoother, quieter and more efficient mode of transport than electric or steam-powered trains, but the many attempts to build them in the late 1800s failed due to financial difficulties.
The first air-powered trains ran above ground, were called atmospheric railways, and briefly offered a serious alternative to steam engines. The vehicles had a cylinder suspended from their underside, which sat inside a slit pipe in the centre of the tracks. The pipe’s slit was covered with bristles and greased leather flaps, making an air-tight seal around the piston: air was then pumped or vacuumed from stations, setting the train in motion.
The first atmospheric railway line, opened in 1844 to connect Dublin and Dalkey in Ireland, was also the most successful, operating for ten years. The train was pulled by vacuum nearly two miles up an incline, achieving speeds of 30 mph; on the much slower return journey, the train simply rolled back down.
Inspired by the Dalkey atmospheric railway, Brunel extended his railway from Exeter to Newton in south-west England with an air-powered section in 1847. Though more efficient than steam power for getting trains up steep gradients, and able to run trains at 70 mph, the pumping stations which had to be situated every two miles were expensive to run. The leather flaps used to seal the pipes dried out and rotted quickly. When lubricated with tallow, they were eaten by rats. After less than a year of operation, the railway was considered a commercial failure and converted to steam power.
Nearly twenty years later, shortly after London’s first steam-driven underground line opened, a railway was built in which the entire train was a piston, fitting tightly inside a cylindrical tube. Thomas Webster Rammell, who had experience building pneumatic tube systems for transporting post, opened the 550 metre long line under London’s Crystal Palace Park in 1864. This was a prototype for a longer line which would connect Waterloo train stain with Whitehall via a tunnel under the river Thames. Though construction began, the 1866 financial crisis led to the project being abandoned.
The most successful pneumatic railway ever built was even shorter, running only 95 metres under Warren Street in New York City, turning a corner into Broadway. Also intended as a demonstration, it was built in 1870 by Alfred Ely Bleach, then publisher of Scientific American. Although extremely popular with tourists, who came to ride its single luxurious carriage out into the tunnel then back again, it failed to secure an investor, and was never extended.
A few abandoned pump houses are all that remain of atmospheric and pneumatic railways today. Had money flowed a little differently, people may have travelled under our cities in smooth, silent tubes instead of rattling trains – but as lines would be unable to emerge above ground, and carriages would be sealed with no windows, perhaps pneumatic railways are best left as a pipe dream.
Keir Little finds pneumatic railways really get him going. He sometimes pushes his own air through the pipes on Twitter @keirwl.