PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 575 



is open and the other closed, as indicated at D, D, the current must also go 

 round, but the car will stop within the station, after which the other gate 

 may be closed, and the state shown at C will be attained. Fig. 2 shows 

 botli gates open and the current going straight along, while fig. 3 shows 

 botii closed, tlic current going round and the station open to the exter- 

 nal atn»os|)here, so that cars may load and unload, passengers get in or 

 out, without interfering with the working of any other part of the rout. 



It is evident, from a careful view of this diagram, that the whole power 

 exerted by the air pump is available in generating a current of air within 

 the tube. There is no air drawn in from the outside to keep up the cur- 

 rent, nor is any air in motion thrown away into the atmosphere, but the 

 air taken from one end of the circuit of tube is driven into the other, thus 

 giving at once compression and exhaustion by the one action of the pump. 

 Since there is a double line of tube there maj'- be travel in both directions 

 at once without the possibility of collision. When a car approaches a 

 station it can be made either to notify the station man or to operate auto- 

 matic divices, so that the farther gate will be shut and the car be stopped 

 in the gentlest manner by impinging on a cushion of air, after which the 

 other gate js closed and the station is opened to the outside. Several cars 

 may move along the track in the same direction, at the same time, without 

 fear of interfering, for tliey would be, as it were, attached to an endless 

 band of air and have to maintain their relative distances, A car may be 

 transferred from the up to the down tube at any station, and the current 

 of air may consequently be maintained always in the one direction. 

 ' The tube may be made of an inexpensive material — wood, burned clay, 

 Roman cement, or anything of which a tube can be made. The stationary 

 power may be steam or water, provided only the engines or water wheels 

 be at suitable distances along ,the track, at say from five to ten miles 

 apart. We see, then, that Ncedham has perfected this new style of loco- 

 motion. Its economy of construction and working can not be surpassed. 

 For safety and speed it is more desirable than any other style of travel for 

 passengers, and its speed should make it the great means of carrying and 

 distributing mail matter, newspapers and parcels. Its peculiar suitable- 

 ness for city locomotion, as not interfering with rights of way or of pro- 

 perty, and giving an admirable means of passing from the business centers 

 to the suburbs, points it out as the best means yet proposed for relieving 

 Broadway and the other crowded thoroughfares of our city. 



Mr. Neediiam's address is 97 East Twenty-third street, New York, and 

 I am confident that any gentleman calling upon him for information upon 

 this plan of locomotion will be allowed a sight of his working model. 



After selecting "City Sewerage" as the next topic for discussion, the 

 Association adjourned. 



American Institute Polytechnic Association, ) 

 April \Zih, 1865. j 



Prof. S. D. Tillman, in the chair; B. Garvey, Secretary. 



The Chairman opened the meeting by saying, that during a recent trip 



