What is "atmospheric railway"

Railroad \Rail"road`\ (r[=a]l"r[=o]d`), Railway \Rail"way`\ (r[=a]l"w[=a]`), n.

1. A road or way consisting of one or more parallel series of iron or steel rails, patterned and adjusted to be tracks for the wheels of vehicles, and suitably supported on a bed or substructure.

   Note: The modern railroad is a development and adaptation of the older tramway.

2. The road, track, etc., with all the lands, buildings, rolling stock, franchises, etc., pertaining to them and constituting one property; as, a certain railroad has been put into the hands of a receiver. Note: Railway is the commoner word in England; railroad the commoner word in the United States. Note: In the following and similar phrases railroad and railway are used interchangeably: Atmospheric railway, Elevated railway, etc. See under Atmospheric, Elevated, etc. Cable railway. See Cable road, under Cable. Ferry railway, a submerged track on which an elevated platform runs, for carrying a train of cars across a water course. Gravity railway, a railway, in a hilly country, on which the cars run by gravity down gentle slopes for long distances after having been hauled up steep inclines to an elevated point by stationary engines. Railway brake, a brake used in stopping railway cars or locomotives. Railway car, a large, heavy vehicle with flanged wheels fitted for running on a railway. [U.S.] Railway carriage, a railway passenger car. [Eng.] Railway scale, a platform scale bearing a track which forms part of the line of a railway, for weighing loaded cars. Railway slide. See Transfer table, under Transfer. Railway spine (Med.), an abnormal condition due to severe concussion of the spinal cord, such as occurs in railroad accidents. It is characterized by ataxia and other disturbances of muscular function, sensory disorders, pain in the back, impairment of general health, and cerebral disturbance, -- the symptoms often not developing till some months after the injury. Underground railroad Underground railway.

   1. A railroad or railway running through a tunnel, as beneath the streets of a city.

   2. Formerly, a system of co["o]peration among certain active antislavery people in the United States prior to 1866, by which fugitive slaves were secretly helped to reach Canada.

      Note: [In the latter sense railroad, and not railway, was usually used.] ``Their house was a principal entrep[^o]t of the underground railroad.''
      --W. D. Howells.

Atmospheric \At`mos*pher"ic\, Atmospherical \At`mos*pher"ic*al\, a. [Cf. F. atmosph['e]rique.]

1. Of or pertaining to the atmosphere; of the nature of, or resembling, the atmosphere; as, atmospheric air; the atmospheric envelope of the earth.

2. Existing or occurring in the atmosphere.

   The lower atmospheric current.
   --Darwin.

3. Caused, or operated on, by the atmosphere; as, an atmospheric effect; an atmospheric engine.

4. Dependent on the atmosphere. [R.]

   In am so atmospherical a creature.
   --Pope.

   Atmospheric engine, a steam engine whose piston descends by the pressure of the atmosphere, when the steam which raised it is condensed within the cylinder.
   --Tomlinson.

   Atmospheric line (Steam Engin.), the equilibrium line of an indicator card. Steam is expanded ``down to the atmosphere'' when its pressure is equal to that of the atmosphere. (See Indicator card.)

   Atmospheric pressure, the pressure exerted by the atmosphere, not merely downwards, but in every direction. In amounts to about 14.7 Ibs. on each square inch.

   Atmospheric railway, one in which pneumatic power, obtained from compressed air or the creation of a vacuum, is the propelling force.

   Atmospheric tides. See under Tide.

An atmospheric railway uses differential air pressure to provide power for propulsion of a railway vehicle. A static power source can transmit motive power to the vehicle in this way, avoiding the necessity of carrying mobile power generating equipment. The air pressure, or partial vacuum (i.e. negative relative pressure) can be conveyed to the vehicle in a continuous pipe, where the vehicle carries a piston running in the tube. Some form of re-sealable slot is required to enable the piston to be attached to the vehicle. Alternatively the entire vehicle may act as the piston in a large tube.

Several variants of the principle were proposed in the early 19th century, and a number of practical forms were implemented, but all were overcome with unforeseen disadvantages and discontinued within a few years.

A modern proprietary system has been developed and is in use for short-distance applications.