THE PNEUMATIC DISPATCH.

Thames Advertiser, Volume VII, Issue 1858, 7 July 1874, Page 3

THE PNEUMATIC DISPATCH.

The London Times gives an Account of' the origin and development. of, the pneu-. matic dispatch system in England, and then goes on to describe pneu-' ■' matio dispatch tube in the heart of'LotK'.vl--don'.-It says:—The pneumatic, tube l , extends . from the London, and jNoi'th- ~ western railway statioiV at Euston Square : to the general post-office in St. Martin's lo Grand. The general station is in Eolborn, where i? alsothe machinery for - - effecting the transit of the trains. Here the tube is divided, so that in effect there are two tubes opening into the station, one from liustou .to Holborn, and the other from the post-office, The length of the tube''tfetwe'en-Üblbom and: Eustonjis ■ 3,080 yards, or exactly, a mile and three-' quarters, a greater length than was ; originally-cohteinplate'di but 1 -w.hich'iwas y* rendered necessary by, the avoidance of -: . certain.property,on the route.. The tubo is of . a flattened horse-shoe sectiohV five feet wide and four, feet six inches high at'the center; having; a sectional, ,area 0f,.. seventeen square .feet. ,Tjhe straight por-. u . ' tions of the line areformed of a'continuous' ; , east iron tube, the curved; lengths being :• :• constructed in brick work,, with a facing of cemeht. The gradients are easy; the two chief are one in forty-five and one in ■>/. sixty, some , portions of the Jine being on • the level.' • Tho sharpest curve' is of 70 '' feet radius. The tube between llolbora and the'post-office is 1,658.in length, or •- ;102 yards'less than a mile, ; 'aad ; is of the - v ,same section and similarly'constructed to ; ■ 'the first length. Two gradients of one in ( fifteen occur ia the post-oiliue sectiou, but"' 'V ' this steep inclination is in no why inimical < : to: the working of the system. ;,The Hoi-. born station is situated at right angles to.=; . the line of the tubes, whioh^are.thereforo, ; turned towards the station, into which each opens. AUthrough trains,- therefore, ; • have to reverse there, aud; this is effected in. a verysimple m inner bya.selfractiag arrangement. , A train, upon its arrival, runs by virtue of its acquired momentum up a short incline, at the summit of wuich it momentarily stops, and tlun q'lickly, ■ descends by gravity.. Inits desoou&it is turned on.toa pair of rails leading .. other tube, into which it enters ' aud through which it continues its journey, the whole process of reversing occupying parely thirty seconds. Trains containing, . goods for Holborn station are rua ■ , ■ down from the top ot the incline on ; to a ii; tiding..' The waggons,'or thoy.r are termed, weigh 22 hundred woiglit, uro 10 feet 4 inches in length, and have -a :, transverse contour conforming to that of the tube.. They are, however, of a slightly smiller area than tho tube itsolt, the difference, about an incn all around, being occupied by a flange ot India i übher, which causes the carrier to fit the tube. . exactly, and so as to form a piston upon •which the air acts, The machinery for-' propelling tho.cirner consists of a steaia engine having a pair of 21-inch cylinders, and With 20-inch stroke. LTiia . engine s drives a fan 22 feet 6 inches in diameter, , and the two are geared, together in suoU, a manner that one revolution .of - tho.! former gives two of the latter; or,, in : lechuioal terms/ the ougiue is geared, afei • two to one with the fan. The trains aw drawn from Euston and the' post-office by ...... exhaustion, and are propelled _ to those points by pressure. The working of thefan/however,is not reversed sosuit,tliose... constantly varying conditionsj'it works.-. continuously, tho alternate action of - sure and exhaustion being governed by valves. The engine takes steam from three Cornish boilers, each 30feetlong,' and 6 feet 6 inches ia diameter. Tolegra- ; phio signaling is carried on between threfSi atjitioaa bj