Tho Br.tisjli pu.itotïiou, wiiiuh i.s ad mittod to bu a model institiition by th people wlio irt) deponiont on iis mini?trations, n in j ftot imfruijuently beou huid up to tdiniruiion bv us, is abont to oonvuv letten ('i- . 1 1 : one part of Lo;i don to :un tliai' liy atinospherio pressuro. Thti tliing .h L'Xixvdlngly simple. A tube !a'(l duv.i bet veen two givci pointe: a 0..:% ol di.n'-n.-io.'is as much Smaller Uifin ihu i ub uu lvi'1 porinit it to slip iiifidu ihd ',]■', i! n'ruilnci'd thereII, and ! ': ■■ ',';.'■!.- ].;fi i-xluiu.-tud of' air. TIiü prcsirre ! iin; (iitsi c :itmoppbere lorres tlio i'aie alon tbu tube, whioh is vui.], and thu cisewith its conten Is f (otters or p:ue1s, id carried swiftly (o i:.s lUstiiiution, Tlie nvöiitiitc ís rat now by any meaiw, even in prautiee, for bot H in England and Tití:::) I t was used to movo railroad triliiis. Hotween Dubün and Kirigs'ton, rii ! aiso betweon j don ;m Ci"oV''l('i, and o tb ei' places ntmospherLe rnilways, as they are callud, ! liave been in operation, Thoy crere not succe3.-fnl, huwuvcr, cbiefly because it was found very cspcusivc to inaintain stationary engincsof powtr euough and ncar cnongh to one anoihor to keep i the tubes snfb'ciently eshausted. The tubes laid for the Lnndon and Croydon Railway wcre seemingly about a fooi in diameter. Such tubos as are re quired fr.r tho lottcr and parcel posts - and even samples of merchandiae aro to be transmiitod by it - will probably not exceed a fortli of that diameter, and as there will be but littlo le&kage oomp:ired with that oí the railway, which required a moving me'xns of communieation witb tbc interior, and therefore while ihe oars rere in motion kept a small portion of the tube open. the tubes for postal and express purposes are not likely to provo difBciilt of complete exbnustion at roasonable expense. Tho distance to be experimented on in London are confined to a few miles, at inost bïx or sevun ; but it is quite probable that, if the plan answers fcr short dia tan C68, improvements in the means of exhauating ttie tube?, and of eoonomizing the exhansting power, wil parmit of the adoption of the pneumatic principie, not only for the couveyance of letters and parcela for short distances, but even of tho more bulky articles for long distances.