578 



PNEUMATIC RAILWAY. 



and for the second Prof. Tyndall proposes that 

 of Calorescence. Dr. Aikin claims the honor 

 of first proposing the experiments which Prof. 

 Tyndall has first successfully executed. 



PNEUMATIC RAILWAY. The Crystal 

 Palace grounds, at Sydenham, England, were, 

 during August, 1804, the scene of a very inter- 

 esting experiment. A series of trial trips on the 

 model Pneumatic Railway, constructed there, 

 under the superintendence of Mr. Rammell, C.E., 

 took place. A brickwork tunnel, about ten feet 

 high by nine feet wide, and capable of admit- 

 ting the largest carriages used on the Great 

 "Western Railway, had been laid with a single 

 line of rails, fitted with opening and closing 

 valves at either extremity, and supplied with 

 all the other requisite apparatus for propelling 

 passenger trains on the pneumatic principle. 

 The tunnel or tube extends from the Sydenham 

 entrance of the grounds to the Armoury, near 

 the Penge-gate, a distance of nearly six hundred 

 yards. The object of laying down this experi- 

 mental line was to afford, both to the scientific 

 world and the travelling public, a practical 

 demonstration of the applicability to passenger 

 traffic of the motive power already employed by 

 the Pneumatic Despatch Company in the con- 

 veyance of letters and parcels. The pneumatic 

 principle of propulsion is very simple. The 

 train is driven along in one direction by a 

 strong blast of air, and drawn back again in 

 the opposite direction by the exhaustion of the 

 air in front of it. The train may be said, in 

 fact, to be blown through the tube on the down 

 journey, and sucked through it on the return 

 journey. It must not, however, be supposed 

 that the passengers are deposited at their des- 

 tination with a sudden jerk. Such an incon- 

 venience is entirely obviated by the mechani- 

 cal arrangements employed. The motion is 

 throughout smooth, easy, and agreeable, and 

 the stoppages are effected gently and gradually. 

 Indeed, when it is considered that the curve in 

 the tunnel is unusually sharp, being of eight 

 chains radius, and that the gradients are as 

 high as one in fifteen (those of Holborn Hill 

 being only one in eighteen), it is surprising that 

 the motion should be so much steadier and 

 pleasanter than ordinary railway travelling. 

 The journey of six hundred yards was perform- 

 ed either way in about fifty seconds, with an 

 atmospheric pressure of only two and a half 

 ounces to the square inch ; but a higher rate of 

 speed, if desirable, can easily be obtained con- 

 sistently with safety. Indeed, one great inci- 

 dental advantage of this species of locomotion 

 is that it excludes all risk of the collisions occa- 

 sionally attendant on railway travelling ; for it 

 is pl?an that no two trains could ever run 

 against each other where all the propelling 

 force is expended in one direction at one time. 

 The worst mishap which it is said could well 

 happen is that, owing to some sudden failure in 

 the machinery, the train might be abruptly 

 brought to a dead stop in the middle of the tun- 

 nel, when the passengers would have to alight 



from the carriages and grope their way as best 

 they could out" of the tube. Such a predica- 

 ment certainly would not be enviable, but it 

 might be more ludicrous than dangerous. 

 Whether in such a contingency there is any 

 possibility of another train being started befor 

 they had safely made their exit, or any risk 01 

 their sharing the fate of frogs placed under an 

 exhausted air-pump, we do not venture to as- 

 sert ; but probably the scientific engineer could 

 guarantee the traveller against any such novel 

 peril. The train used consisted of one very 

 long, roomy, and comfortable carriage, resem- 

 bling an elongated omnibus, and capable of ac- 

 commodating some thirty or thirty-five passen- 

 gers. Passengers enter this carriage at either 

 end, and the entrances are closed with sliding 

 glass doors. Fixed behind the carriage there 

 is a framework of the same form, and nearly 

 the same dimensions, as the sectional area of the 

 tunnel ; and attached to the outer edge of this 

 frame is a fringe of bristles forming a thick 

 brush. As the carriage moves along through 

 the tunnel the brush comes into close contact 

 with the arched brickwork, so as to prevent 

 the escape of the air. With this elastic collar 

 round it, the carriage forms a close fitting piston, 

 against which the propulsive force is directed. 

 The motive power is supplied in this way : At 

 the departure station a large fan-wheel, with an 

 iron disc, concave in surface and twenty-two 

 feet in diameter, is made to revolve by the aid 

 of a small stationary engine at such speed as 

 may be required, the pressure of air increasing, 

 of course, according to the rapidity of the revo- 

 lutions, and thus generating the force necessary 

 to send the heavy carriage up a steeper incline 

 than is to be found upon any existing railway. 

 The disc gyrates in, an iron case resembling that 

 of a huge paddlewheel; and from its broad 

 periphery the particles of air stream off in 

 strong currents. When driving the air into 

 the upper end of the tunnel to propel the down- 

 train fresh quantities rush to the surface of the 

 disc to supply the partial vacuum thus created ; 

 and, on the other hand, when the disc is ex- 

 hausting the air in the tunnel with the view of 

 drawing back the up-train, the air rushes out 

 like an artificial hurricane from the escape 

 valves of the disc case, making the adjacent 

 trees shake like reeds and almost blowing off 

 his feet any incautious spectator who approaches 

 too near it. 



When the down journey is to be performed 

 the breaks are taken off the wheels, and the 

 carriage moves by its own momentum into the 

 mouth of the tube, passing in its course over a 

 deep air-well in the floor, covered with an iron 

 grating. Up this opening a gust of wind is sent 

 by the disc, when a valve, formed by a pair of 

 iron doors, hung like lock-gates, immediately 

 closes firmly over the entrance of the tunnel, 

 confining the increasing atmospheric, pressure 

 between the valve and the rear of the carriage. 

 The force being thus brought to bear upon tho 

 end of the train, the latter, shut up within tiit< 



