considered the limiting factor. On hearing of the success of the Dalkey railway, the French minister of public works (M. Teste) and under-secretary of state (M. Le Grande) dispatched M. Mallet, inspecteur général honoraire des Ponts et Chaussées, to Dalkey. He wrote an exhaustive technical evaluation of the system installed there, and its potential, which included the results of measurements made with Joseph Samuda. It was through his interest that the Pereire brothers to adopt the system for an extension to Saint Germain itself, and construction started in 1845, with a wooden bridge crossing the Seine followed by a twenty-arch masonry viaduct and two tunnels under the castle. The extension was opened on 15 April 1847; it was 1.5 km in length on a gradient of 1 in 28 (35 mm/m). The traction pipe was laid between the rails; it had a diameter of with a slot at the top. The slot was closed by two leather flaps. The pumps were powered by two steam engines with a capacity of 200 hp, located between the two tunnels at Saint-Germain. Train speed on the ascent was . On the descent the train ran by gravity as far as Pecq, where the steam locomotive took over for the run to Paris. The system was technically successful, but the development of more powerful steam locomotives led to its abandonment from 3 July 1860, when steam locomotive ran throughout from Paris to Saint Germain, being assisted by a pusher locomotive up the gradient. This arrangement continued for more than sixty years until the electrification of the line. A correspondent of the Ohio State Journal described some details; there seem to have been two tube sections: An iron tube is laid down in the centre of the track, which is sunk about one-third of its diameter in the bed of the road. For a distance of 5,500 yards the tube has a diameter of only 1¾ feet [i.e. 21 inches], the ascent here being so slight as not to require the same amount of force as is required on the steep grade to Saint Germain, where the pipe, for a distance of 3,800 yards, is 2 feet 1 inch [i.e. 25 inches] in diameter. The steam engines had accumulators: To each engine is adapted two large cylinders, which exhaust fourteen cubic feet of air per second. The pressure in the air cauldron (claudieres) attached to