MECHANICS AND USEFUL ARTS. 63 



vulcanized India-rubber, about 12 inches wide and 5 inches thick. 

 This soft and clastic substance not only carries the o-rcat wei"-ht 

 of the steamer (between 4 and 5 tons) without injury, but it is 

 not even marked by flints and other sharp objects over which the 

 wheels may pass; the wheels do not in the least sink into the 

 road, and jDass over the surface stones without crushing- them. 

 These tires somewhat resemble the feet of the elephant and 

 camel, whose soft cushions it is well known are much less injured 

 bv hard roads than solid hoofs. As it floats aloni^: on the India- 

 rubber tires, neither sinking nor crushinir, much less power is 

 required to propel it than if it had rigid tires, and scarcely any 

 more on soft or loose roads than on the best-paved streets. Ex- 

 periments with an engine of this kind are given as follows in the 

 *' Civil Engineer and Architect's Journal," January, 1868: — 



" The trials commenced by running the road steamer across a 

 soft grass field, and it was afterward taken across a part of the 

 field which had just been covered with loose earth to the depth of 

 1 or 2 feet, and run straight across, and then back through the 

 deep, soft soil. The weight of the road steamer is between 4 and 

 5 tons ; and 3^et the wheels, in passing over the loose earth, com- 

 pressed it so little that a walking-stick could easily be pushed 

 down in the track of the wheels without any exertion. After 

 various evolutions, showing the ability of the road steamer to run 

 where there were no roads, it passed out into the street, and, 

 taking a large omnibus full of passengers in tow, it proceeded up 

 the Bonnington road, where it took a large wagon, weighing, with 

 its load of flour, about 10 tons, up a steep lane full of holes and 

 ruts, and rising with a gradient of 1- in 20. It was obvious that 

 the road steamer was able to do a great deal more than it had to 

 do in this trial. The bite on the road is something marvellous, 

 and the easy way in whic h it floated along on its soft and elastic 

 tires was very curious. When riding on the road steamer, the 

 feeling is like Avhat would be experienced in driving over a 

 smooth, soft grass lawn. There is, absolutely, no jarring at all. 

 There was no appearance of wear on the India-rubber tires. 

 The original surface which the rubber had when it left the manu- 

 factor}?- is still visible. The engine is destined for Java, where 

 it will be employed in drawing trains of wagons between two 

 ports." 



NEW ELECTRICAL ENGINE. 



This engine, the invention of Mr. Laban C. Stuart, as exhibited 

 in New York, consists essentially of a horizontal central axis 

 about 3 feet in length, armed with a series of electro-magnets, 

 and having opposed to them a set of stationary magnets. With 

 a Bunsen's battery of 40 cells, the axis revolves 500 times per 

 minute. When connection was made with a pump, a simple cal- 

 culation showed the working power of the apparatus to be one- 

 tenth of a horse-power. 



According to the report of the sub-director of the ^.coles im- 

 periales cfarts et metiers^ the most efiicient electrical engine in 



