Page:Popular Science Monthly Volume 88.djvu/364

 336

Railroad Warning for Motorists

IN order that motorists who happen to be unfamiUar with the dangers that lie in their road on the approach to a railroad crossing which is near

��Day or night this roadside signal guards the wary autoist against the dangers of a grade crossing

Lutherville, Md., a railroad company Avhose tracks run to that city has installed warning posts which can be plainly seen day or night. After dark, a powerful electric lamp behind a re- flector illuminates the warning posts which can tells them that a dangerous railroad crossing exists three hundred and fifty feet ahead of them. The cross arms can be seen and read easily in the daytime, as they are placed in a con- spicuous position. A bright red glass in back of the lamp, the conventional danger signal, makes the warning sign doubly effec- tive. The scheme w^as de- vised by Walter R.Moulton, an illuminating engineer.

��Popular Science Monthly

Sharpening Drills by Air

AT quarries and mines, one of the most time-consuming tasks is the regrinding of dull drills. Expert forges are required if the w^ork is done prop- erly. To obviate the large amount of time spent in this way, a pneumatic drill sharpener has l:)een installed in some m i n e s and quarries. It shortens the task of drilling to a fraction of the time formerly re- quired when the job w^as done by hand. The drill heads are heated to the proper temperature and placed between dies, and the pneiunatic hammer shapes the head in a few sec- onds. Various patterns of dies are em- ployed for various drill heads.

A Key Marker.

A HANDY way to mark keys of the Yale type so that they are easily distinguished in the dark is to insert an ordinary office paper rivet in the hole in the handle of one of the keys and flange it in the usual way with the punch. There is no mistaking the "feel" of a key so marked.

����Compressed air is one of the most powerful mechanical agencies of to-day. Here it is harnessed to the job of sharpening rock drills

�� �