Page:Popular Science Monthly Volume 92.djvu/366

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Popular Science Monthly

Wire-Netting Instead of Wood for Surgical Splints

ANEW kind of surgical splint in which galvanized wire-netting takes the place of wood, has been put on the market. It has been tried and offers many advantages. The steel entering into the construction of this woven wire splint is so tempered that it can be molded by hand. Being gal- vanized, the wire is sterilized and at the same time • welded into a single piece that cannot fray out at loose ends. As it is porous, it allows a certain amount of evaporation and air circulation to the dressings beneath, which wood or plas- ter does not. The

splint comes rolled like a bandage and is lighter and less bulky than wooden splints.

Two methods of using the wire netting splint are shown in the illustration

Track Insulation Stops the Trains in This Automatic Control System

THERE are now many methods for automatically stopping a train which has run past a stop signal. But none is simpler than the Gray-Thurber system. No ramps, third rails nor other appliances on the track are required. The only change in the ar- rangement of the track that is necessary in the new sys- tem is a single piece of in- sulation, placed at the rail joints near the sema- phore sig- nals.

Between the insu- lated rail

ends at these joints is a make-and-break relay operated by the same current as the semaphore. In case of danger, the break- ing of this current raises the semaphore arm to the "stop" position and, at the same time, it opens the relay. The two rail ends are there- fore electrically dis- connected from each other.

The valve control- ling the brake is normally held in- operative when there is a current going through the valve re- lay. This current flows from a battery on the locomotive, through the locomo- tive wheels, the rails, the wheels of the tender, and from thence to the relay. But when the train passes a danger sig- nal, the disconnected rails break this cir- cuit. The relay is demagnetized and a spring opens the valve of the air brakes, stopping the train.

When the semaphore arm goes up, the track relay opens. Should the train try to pass the disconnected rails, the valve relay is demagnetized and. the brakes are set

The circle shows the location of the valve relay which sets the brakes on the train when its current is shut off