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HOW WE USE LIGHT 



Galloway 



How many different kinds of stop lights have you seen ? It would be a good thing 

 to have these signals uniform for all parts of the country. Can you see why ? 



image in the back of the eye excites the proper nerve end- 

 ings so that the brain can interpret the image and in this 

 way we see objects. 



Colored Signal Lights. The engineer depends upon 

 colored lights to tell him if there is a clear track ahead. 

 Where other trains use the same track and where switches 

 may lead to branch tracks, a green light is a signal that 

 the track is clear and safe. A red light is the signal for 

 danger. On boats you see green lights on the starboard 

 or right side and red lights on the port or left side. If we 

 travel by train or water, our safety depends greatly upon 

 the watchfulness of the pilot or engineer and his care in 

 heeding signals. Our most common use of signal lights is 

 the traffic signal and automobile tail light. Here again 

 red is the danger sign and green the signal to pass. In 



