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 



