MECHANICS AND USEFUL ARTS. 29 



is set behind the first leaf to sustain the current of air from the inside, 

 to perpetuate the partial vacuum. There are ventilator cones in the 

 roof, which prevent sparks from entering, but allow a fresh supply of 

 air to enter the car continually. Scientific American. 



SELF-ADJUSTING RAILROAD SWITCH. 



MR. AMOS HODGE, of North Adarns, Mass., has recently invented a 

 self-adjusting switch, which is highly recommended. The manner of 

 accomplishing so important a result is very simple, and requires but 

 very little addition to the switches now in use. The sliding section of 

 the track is moved by springs, and is kept in its place by a spring bolt. 

 When the train approaches the main track from any side track, the 

 first car or engine passes over an inclined plane, on the section preced- 

 ing the slide, which pushes forward a connecting bar, on the end of 

 which is a cam, which moves the slide to that track, and by a simple 

 attachment keeps it there until the last car leaves the slide, when it re- 

 turns to the main track. Mr. H. has also designed that by placing a 

 wheel or bearing on each side of a locomotive, the engineer can run 

 to any side track he chooses, by depressing the wheel (or bearing) on 

 the side he wishes to turn out. One single feature in the invention is 

 worth remembering it never will run a train off the track from being 

 placed wrong. North Adams Transcript. 



RAILROAD IMPROVEMENT. 



THE American Railroad Journal furnishes the following description 

 of an improvement of Mr. J. S. French, whereby a locomotive was en- 

 abled to ascend and descend a grade of 200 feet to the mile. The ends 

 of the sills are cut off square with the string-pieces ; the rail, six inches 

 wide and three fourths of an inch thick, is placed upon the string- 

 pieces, and extends outwards two and a half inches, thus affording an 

 under surface against which a pair of rollers [the simple principle of the 

 whole invention] are pressed. These rollers or wheels are suspended 

 from the engine, a little in advance of the driving wheels, and are 

 pressed against the extended rail by a lever, by the regulation of 

 which any amount of adhesion may be obtained. This mechanical ad- 

 hesion has the advantage of being graduated to circumstances ; for on 

 running on a level but little adhesion is required, and on reaching any 

 inclined surface, it is put on in a quantity requisite for ascending, and 

 no more. Thus are avoided the effects of weight in a great measure ; 

 whereas, on the ordinary principle, much dead weight is put on, only 

 to be made use of at certain points, and destroy ing the road on every 

 passage over it. 



In an experiment made at Richmond, Va., an engine, constructed 

 on the above principle, weighing three and a half tons, drew a passen- 

 ger car, with 100 passengers, up a grade of 200 feet to the mile, at the 

 rate of ten miles per hour. 



PROGRESS OF RAILWAYS IN THE UNITED STATES. 



A CORRESPONDENT of the American Railway Times furnishes a state- 

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