ATMOSPHERIC RAILWAY. About 1840-45 great in terest was excited by a method of propelling railway trains through the agency of atmospheric pressure. Various inventors worked at the realization of this idea. On the system worked out in England by Jacob Samuda and S. Clegg a continuous pipe or main was laid between the rails, and in it a partial vacuum was maintained by means of air pumps. A piston fitting closely in it was con nected to the leading vehicle of the train by an iron plate which passed through a longitudinal groove or aperture running the whole length of the pipe. This aperture was covered by a valve consisting of a continuous strip of leather, strengthened on each side with iron plates; one edge was fastened while the other was free to rise. Connected behind the piston was a frame carry ing four wheels which lifted and sustained the continuous valve for a distance of about 15 feet. Thus the piston, having atmos pheric pressure on one side of it and a vacuum equal to 15 or 16in. of mercury on the other, was forced along the tube, taking the train with it. It was installed on about two miles of line between Kingstown and Dalkey (Ireland) in 1843 and worked till 1855; it was also tried on the London and Croydon and on the South Devon lines, but was soon abandoned. (See PNEUMATIC DIS PATCH. ) For further particulars see three papers by J. Samuda, P. W. Barlow and G. Berkeley, in Proc. Inst. C.E., 1844 and