Proceedings of the Polytechnic Association. 915 



ounces per square inch, but pressures of three quarters of a pound are 

 within reach. The cost of working, including engine, fuel, attend- 

 ance, and all establishment charges, is found to be less than one penny 

 per ton per mile. Many persons have availed themselves of the nov- 

 elty of a ride through these tubes in total darkness, from Euston to 

 Holborn and return. The time usually occupied is five minutes. A 

 traveller says : 



The only inconvenience experienced was at the commencement and 

 termination of tlie journey, where a sensation was felt in the ears 

 very similar to that which occurs on descending in a diving bell. 



What is Proposed to be Done. 

 Many of our readers will remember the working section of a 

 pneumatic railway for passengers at the American Institute fair, in 

 October, 1867, which fully demonstrated the simplicity and the 

 applicability of this power. In the elevated railway and pneumatic 

 dispatch combined, Mr. Barnum only proposes at first to apply this 

 principle to mail and parcel transit through the tubes, operating the 

 passenger cars by light dummy engines, placed in the rear of each, 

 so constructed that the machinery is out of view, there being neither 

 toothed gears, bell, or whistle, and no pufiing noise or visible escape 

 of the exhaust-steam ; the fuel used being selected, with a view of 

 making little or no smoke. These cars can run easily around a curve 

 of thirty feet radius, so the road may be adapted to the streets on tlie 

 margin of our city. It is claimed that this route proposed will largely 

 accommodate passenger transit between the extreme upper and lower 

 ends of Manhattan island ; that it will add twofold to the amount 

 of parcel express matter, and double or quadruple travel in a short 

 period of time. The surftice rails can be left for heavy goods traffic, 

 wliich must always be increasing about the shipping, the markets, 

 and the ferries. N"© man, however sanguine, believes that an under- 

 ground or tunnel will be constructed from City Hall to Central Park 

 in less than five, nor from the battery to Harlem in less than ten years. 

 An elevated railway could be built on both sides of the city in less 

 than two years. 



The Cost. 

 The London tunnels, indudrng right of way, stations, and equipments 

 cost over $5,000,000 per mile. The nature of the dirt and the 

 difliculties there encountered are altogether different from those 



