28 ANNUAL OF SCIENTIFIC DISCOVERY. 



strikes the plug and is thrown back, causing the trigger to release its 

 hold of the wheels, which, rapidly revolving, cause repeated strokes of 

 the hammer to be given the bell. This, of course, is notice in all cases 

 to stop the train. Instead of the wheels and bell, the trigger may com- 

 municate with a steam-cock, and the alarm thus be given by means of a 

 whistle. The model is made to show the operation in either case. It 

 is intended for every train to be supplied with one or more cross-bars, so 

 that if any accident happen, not in the vicinity of a station, whereby 

 the track is obstructed, and cannot be cleared in season for the passage 

 of the next train, a cross-bar may be laid upon the track, on either side 

 of the accident, at sufficient distance therefrom to notify such approach- 

 ing train of the danger. So at every station, and in the vicinity of 

 drawbridges, it is intended that cross-bars should be kept, to be used as 

 occasion may require. 



RAILROADS WITHOUT RAILS. 



IN the French Department of the Great Exhibition, a curious system 

 of locomotion was represented, which is, however, only the modification 

 of a plan exhibited in London many years since. It is a railroad with- 

 out rails. In the English invention there were pairs of wheels fixed on 

 the road at stated distances, which were to be kept in motion by sta- 

 tionary engines ; the power being communicated by a band passing 

 from the engine, and connected with a great number of wheels. The 

 rails were fixed to the bottom of the carnages, and were made long 

 enough to have always a bearing on two of the wheels at least. When 

 the system of the wheels was put in action, the carriages were pro- 

 pelled by the bearing which the rails beneath had on the peripheries. 

 One of the advantages of this plan was, that single carriages instead of 

 trains could be started, and at very short intervals, without danger of 

 collision. In the French modification of the invention, the principal 

 difference consists in the means of giving motion to the wheels. Instead 

 of connecting the series with one long endless driving band, there are 

 numerous short endless chains connected with the axles of only two 

 pairs of wheels, so that the motion of one pulls the chain that propels 

 the next. The model road exhibited was on a steep incline, for the 

 purpose of showing that this method of propulsion is applicable to the 

 ascent of hills. 



IMPROVEMENT IN RAILROAD CARS. 



AN unproved ventilating apparatus has been recently attached to rail- 

 road cars, built by Messrs. Bradley & Rice, of Worcester, Mass. The 

 windows are so constructed that they are made to act the part of ven- 

 tilators, by having two leaves ; the front one is set to stand out, with its 

 inner end forming the apex of a cone, the outside being the base. The 

 ah' impinges on this window, as it is set angularly to the side of the 

 car, and it therefore forms a partial vacuum at its outer edge. This 

 draws the air from the inside and thoroughly ventilates the car, allow- 

 ing nothing to come in from the outside. The other leaf of the window 



