MECHANICS AND USEFUL ARTS. 41 



one steam-chest and valve, which produce a perfect unity of action in 

 both systems." Scientific American. 



Oblique Railroad Wheels. One of the most interesting sights in Paris, 

 is the railroad from the Barrier d'Enfer to Sceaux. It is but seven miles 

 long, and was built as an experiment upon a new system of wheels. The 

 engine, tender, and hindermost car of the train are furnished with oblique 

 wheels, under the ordinary upright ones. AVhere the track is straight, 

 these do not touch the rails ; but at the curves they come into play, rat- 

 tling along the inner edge of the rails, and preventing the train from 

 running off the track. The road was, therefore, made purposely tortuous, 

 and the most sudden and seemingly dangerous bends were introduced at 

 frequent intervals. The two stations are circular, and the train, as it 

 receives its passengers, is doubled up into a ring of oO feet radius. The 

 smallest curve upon the road is 68 feet radius, and over this the train goes 

 at full speed. The corners of the cars are cut off, so that the vehicles, in 

 following the curves, do not infringe upon each other. Sceaux is upon 

 an eminence, which the road ascends spirally, with something like a mile 

 of track it only going, in advance, a hundred feet. The invention 

 which, by the way, is ten years old has proved, practically, very suc- 

 cessful ; but it has never been applied to any extent. 



Ruttans Car Ventilator. In this invention, which is highly commended, 

 the fresh, pure air is caught, by a projecting box or cap on the centre of 

 the roof, and conveyed down a passage on the inside of the car, through 

 the floor, to a shallow tank beneath. Spreading out here, it deposits its 

 cinders, ar.d, to a considerable degree, its smoke and dust, after which it 

 rises through the stove which is of peculiar construction, on the princi- 

 ple of a hot-air furnace and is projected, in every direction, from the top 

 of the stove into the car. The opening for its escape again, from the 

 interior to the open air, is near the floor, and the current of warm, foul 

 air, is conveyed under the entire length of the car, completely protecting 

 the feet of the passengers from the influence of the external cold. Having 

 completed this circuit, it is carried up through suitable passages, and 

 allowed to escape from a cap on the top. These ejecting caps are at each 

 end of the car, to allow of running in each direction, and are closed by 

 light, self-acting valves, opening outward. The current induced by the 

 rapid motion through the air, closes the valve on the forward, and opens 

 that on the hinder one, and each valve is so balanced, by a short loaded 

 lever or tumbling-bob, that the weight tends equally to hold either open 

 or closed. It results from this contrivance, (which may appear paradoxi- 

 cal to some, but is easily constructed by any mechanic,) that whichever 

 position the valves may assume in the most rapid motion, will be main- 

 tained until the motion is reversed. The openings from, these ejectors or 

 exhausting boxes, into the cars, are controlled by hand, but the only effect 

 of exhausting direct from either end, may be an unpleasant cooling of the 

 floor. 



