it. A pumping station ahead of the train would pump air from the tube, and air pressure behind the piston would push it forward. The Wormwood Scrubbs demonstration ran for two years. The traction pipe was of 9 inches diameter, and a 16 hp stationary engine was used for power. The gradient on the line was a steady 1 in 115. In his treatise, described below, Samuda implies that the pipe would be used in one direction only, and the fact that only one pumping station was erected suggests that trains were gravitated back to the lower end of the run after the atmospheric ascent, as was later done on the Dalkey line (below). Many of the runs were public. Samuda quotes the loads and degree of vacuum and speed of some of the runs; there seems to be little correlation; for example: 11 June 1840; 11 tons 10 cwt; maximum speed 22.5 mph; 15 inches of vacuum 10 August 1840: 5 tons 0 cwt; maximum speed 30 mph; 20 inches of vacuum. Competing solutions There was enormous public interest in the ideas surrounding atmospheric railways, and at the same time as Samuda was developing his scheme, other ideas were put forward. These included: Nickels and Keane; they were to propel trains by pumping air into a continuous canvas tube; the train had a pair of pinch rollers squeezing the outside of the tube, and the air pressure forced the vehicle forward; the effect was the converse of squeezing a toothpaste tube. They claimed a successful demonstration in a timber yard in Waterloo Road. James Pilbrow; he proposed a loose piston fitted with a toothed rack; cog wheels would be turned by it, and they were on spindle passing through glands to the outside of the tube; the leading carriage of the train would have a corresponding rack and be impelled forward by the rotation of the cog wheels. Thus the vehicle would keep pace with the piston exactly, without any direct connection to it. Henry Lacey; conceived a wooden tube, made by barrel-makers as a long, continuous barrel with the opening slot and a timber flap retained by an india-rubber hinge; Clarke and Varley; proposed sheet iron tubes with a continuous longitudinal slit. If the tubes were made to precision standards, the vacuum would keep the slit closed, but the piston bracket on the train would spring the slit