MECHANICS AND USEFUL ARTS. 57 



PNEUMATIC RAILWAY. 



The Pneumatic Dispatch Company have successfully applied 

 the jjrinciplo of atmospheric pressure to the conveyance of letters 

 and merchandise, and thus aiforded an opportunity of showing 

 that human beings may continue without inconvenience in a closed 

 tube. This removal of an ajjparently insuperable objection to 

 atmospheric propulsion is very important, since, witli a pneu- 

 matic railway, the danger of accident is reduced almost to nothing. 

 Collisions are imjiossible ; and, as the train cannot get off the line, 

 the greatest velocity is unattended with danger. The view of 

 external objects is excluded ; but tins privation is little greater 

 than that experienced on ordinary railways, where there are many 

 cuttings, tunnels, and interposed objects. With an atmospheric 

 railway, the exjjcnse of construction and maintenance are greatly 

 diminished ; steep gradients and sharp curves cease to be objec- 

 tionable, since an ascent of one in fifteen, or a curve of eight 

 chains radius, causes no inconvenience, and great facilities are 

 afforded by it for passing under rivers. 



The tubes of the Pneumatic DisiDatch Company have been in 

 operation for more than three years, in conveying parcels ; and the 

 applicability of the system to carrying passengers has been amply 

 demonstrated. The line of the Waterloo and Whitehall Railway 

 is to cross the river just above Hungerford Bridge. The tube is 

 made in four sections of two hundred and thirty feet length each. 

 The ends of these will be connected by being introduced into 

 junction cliambers foiiued in the bi'ick piers on whicli they rest, 

 the joint being made water-tight. These piers do not rise as high 

 as the present river bottom, and a channel will be dredged across 

 the river to receive the tubes, though the principal weight will be 

 supported on tlie piers. One of tlie tubes is now completed at 

 the ship-building yard of Messrs. Samuda, at Pojolar, five miles 

 below its intended situation. It is twelve feet nine inclies in diam- 

 eter inside, and is of tliree-quarter-inch boiler-plate, surrounded 

 by four rings of brick-work, which is firmly held by cement and 

 flanged rings riveted to the plates. Its weight, as it lies, is nearly 

 one thousand tons. To convey it to its destination, the ends are 

 to be closed by bulkheads, and then, having a buoyancy when 

 in the water of about tin-ee hundred tons, it will be floated up the 

 river and brought into position over its piers. An inner ring of 

 brick-work will then be built inside it, and just enough water 

 admitted to sink it upon its foundation. The joints between tlie 

 tubes and piers will then be made water-tight, and the bulkheads 

 removed from the ends of the tubes. The four tubes will thus form a 

 great sub-aqueous bi-idge of four spans of two hundred and twenty- 

 one feet each, the tubes resting in a channel dredg-cd across the 

 bottom ot the I'lver, but being chiefly supported upon massive 

 piers which do not rise even to the river bottom. The coflter-dam 

 at the Whitehall end of the line is no less than fifty-three feet 

 deep. 



When the underground tunnel was finished from Holborn to 

 Easton Station, a distance of two miles, a train of goods with an 

 attendant was sent through the whole distance in five minutes. 



