Procbedings of the P olttechnic Association. 911 



tions for sewers and gas pipes, and the frequent repairing of streets 

 are entirely absent. Signals and signal men at any angle of the road 

 will be obsolete ; street corners or feiTy landings may be chocked 

 ■with a hundred carriages, pedestrians may be endangered by the rush 

 of a score of iire engines, the elevated cars with all their passengers 

 will still pursue the even tenor of their way. 



The Pneumatic Tube. 

 It is claimed that the combination of the pneumatic tube with the 

 elevated railway renders this structure, both for city travel and for 

 mail and parcel dispatch, a most compact, complete and admirable 

 system. On whatever route the establishment of a line of cars for 

 transportation of persons is required, there exists an equal demand 

 for a rapid and regular traffic in mails, express, market, package, 

 parcel and other light matter. The pneumatic way has not yet been 

 introduced in America, either for the transmission of express or mail 

 matter. But a power so simple and practicable, and which has been 

 reduced to a perfect success in Europe, cannot much longer remain 

 untried in our own country. By this application of an invention of 

 Mr. E, P. ISTeedham, of the firm of Carhart & Needham, of this city, 

 I have taken another step in the development and introduction of 

 atmospheric pressure as a motor. 



How THE Tube is Operated. 

 With the railway the tube serves a double office, viz. : That of con- 

 stituting a foundation for the truss-work in supporting and bracing 

 the rails, and that of operating an endless current of air. The models 

 operandi of dispatch business is by sending through the tube series 

 of piston carriages or boxes, laden at each station with • packages 

 assorted and destined for other stations. The diameter of the piston 

 carriages being less than that of the tube, and their support being 

 upon two wheels, one at either end, they are driven through the tube 

 at the same rate of speed (less slight friction and leakage) as is 

 imparted by stationary engines to the current of air. This pneu- 

 matic dispatch is thus adapted for the rapid transmission of mail bags, 

 merchants' parcels, city papers, loaded market basket, books, bundles, 

 boxes, crates and all packages which can be placed within a carriage 

 eighteen or twenty inches in diameter, and four to six feet in length. 

 All carpet-bags, valises, and bundles which may be daily brought to 

 the stations by thousands of passengers, will be dispatched through 



