Proceedings of the Polytechnic Association. 927 



is reversed, the opposite result is, of course, produced ; the volume 

 of air then taken from the surrounding atmosphere is poured in a 

 resistless stream against the piston or flange of the car, M'hich flies 

 before. it back to its starting place. This construction of wheel is the 

 invention of Mr. Beach, and is now for the first time put to practical 

 test on a large scale. We hope to be able to chronicle, in a few days, 

 that the result has realized tlie best wishes of our fellow citizen. It 

 would be most gratifying to learn that, so early in the race of pneu- 

 matic railroad construction, there was such promise of our taking the 

 lead at a single bound. The construction of this apparatus, and that 

 about to be described, was done by tlie Holske Machine Company, 

 and was superintended by Mr. W. T. Holske and Mr. Beach person- 

 ally. • 



The Pneui*iatic Postal Dispatch Tube at the Fair. 



Mr. Alfred E. Beach also exhibited at the fair a section of a postal 

 dispatch, tlu'ough which a truck for the conveyance of mail matter is 

 drawn or propelled in the same manner as above explained. A 

 smaller fan is used for this tube. The tube itself is square, as are the 

 trucks which pass through it. In connection with this apparatus is 

 an ingenious automatic arrangement, showing how mail matters, 

 received at difterent post-ofiice depots along the route, may be kept 

 separate and so delivered, and in like manner can a correct delivery 

 at each station of outgoing mails be effected. This is possibly the 

 most interesting feature of this most attractive exhibition. The lamp- 

 post rising from the middle of the tube represents a street depository, 

 having in its base a pair of rotary letter boxes. Every time the car 

 passes the letter boxes one of these is turned, and its contents drop 

 into the passing car. When the car returns, the other box is operated 

 and its contents collected in like manner. Thus, the car, when pass- 

 ing irp town, collects all letters destined in that direction, having been 

 dropped into the receiver of the lamp-post; returning, the down town- 

 letters are collected from their particular box, into which they have 

 been dropped advisedly from above. 



Projects. 



On the success of these practical tests under the auspices of the 

 American Institute no doubt will depend in a measure whether we 

 shall have any immediate realization of the several projects in view, 

 including not only the establishment of passenger traffic and the 



