CHAP, in.} A TMOSPHERIG RAIL WA YS. 



is old ; it goes back to the first experiments of the inventor of the 

 air-pump, Otto von Guericke. In 1810, a Swedish engineer, 

 Medhurst proposed to transport merchandise, parcels, and letters, in 

 a tube in which a vacuum was made ; then, to communicate the 

 movement of the piston to carriages passing outside the tube. In 

 1824, an Englishman, Wallance, had the idea of transmitting 

 atmospheric pressure directly to the carriages which must then 

 travel in the interior of the tube where the vacuum is produced. 

 The first atmospheric railway was constructed in 1848, in Ireland, 

 nearly three kilometres in length, between Kingstown and Dalkey. 

 The engineers Messrs. Clegg and Samuda again took up Medhurst's 

 system, with improvements. Many other trials were made in 

 England and in France, and on part of the Paris line to Saint- 

 Germain. In the present day, all atmospheric railways have been 



Fio. 44 Pneumatic tube of the atmospheric railway of Sfaint-Gerniain. 



abandoned, not that the mechanical working has proved bad, but 

 because, in an economical point of view, this mode of traction has 

 turned out inferior to that of locomotives ; it was much too ex- 

 pensive. The invention of mountain-locomotives for ascending 

 steep inclines has consequently forced the plan of which we have 

 just spoken to be abandoned. 



Fig. 44 represents a section of the tube (of sixty-three centi- 

 metres diameter) in the interior of which the piston travels, in the 

 atmospheric railway of the Pecq at Saint-Germain. This tube, fixed 

 in the centre of the railway, was pierced by a longitudinal slit 

 through which the metal plate or rod fastening the piston to the first 

 carriage passed. In front of the piston, that is, on the side of the 

 vacuum, the slit was closed by a band of leather furnished with short 

 iron plates acting as a valve, and a series of rollers of decreasing 



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