The Electric Dog and How He 

 Obeys jid^His Flashlamp Master 



The electric dog and its master. A pocket flashlight is the magic 

 wand which it obeys 



THE electrical dog, which Mr. John 

 Hays Hammond. Jr.., and I de- 

 signed, and which has received 

 much pubHcity, has no tail to wag and 

 no voice to bark with, but he can follow 

 a person about in a most surprising way. 



Like the sunflower that follows the 

 sun in its path across the heavens, my 

 first apparatus was capable of turning 

 itself only to face the object that stimu- 

 lated it. " But a great difficulty had to 

 be overcome. The stimulant was light, 

 and sometimes the dog saw too much 

 light, so that he behaved occasionally in 

 an astonishingly erratic manner. 



Just how grave a difficulty this dis- 

 obedience really is. was illustrated by an 

 amusing incident during a demonstration 

 at a Chicago theater. 



The dog was ready to spring into ac- 

 tion, but when the stage was lighted, in- 

 stead of obeying the flashlight held in 

 my hands, the dog insisted on paying at- 

 tention to a very alluring but not thickly 

 clothed young woman painted on the 

 scenery near by. It seems that the re- 

 flected light from the painting was 

 sufficiently brilliant to compete with the 

 flashlight and to cause the dog to creep 

 to this fairer attraction with a directness 

 which was almost uncanny. 



To all practical intents and purposes. 



the electrical dog is a dead dog until ex- 

 cited by an external light ray — usually a 

 pocket flashlight, held in the hand. Fas- 

 tened to the front of a squat, oblong box 

 on three roller-like wheels, are two great 

 lenses, much out of proportion to the 

 rest of the dog's make-up. These are the 

 eyes through which the dog receives his 

 intelligence. Behind the lenses are two 

 extremely sensitive cells containing the 

 black, wax-like selenium. Because of the 

 importance of this substance in the dog's 

 behavior, the mechanical animal has re- 

 ceived its nick-name, "Seleno." A pe- 

 culiarity of selenium is that it is sensi- 

 tive only to light rays ; or, to put the 

 facts a little more technically, selenium is 

 a non-conductor of electric currents un- 

 til it is struck by light, when it becomes 

 a conductor. Located behind the selen- 

 ium eyes is an arrangement of relays, 

 batteries, magnets and a motor. When a 

 beam of light strikes one of the selenium 

 cells, it causes a relay to be operated 

 which, in turn, causes current to flow 

 through one of the magnets controlling 

 the steering wheel. The driving motor 

 starts, and the dog is under way. Shift 

 the light so that it strikes the other selen- 

 ium eye and the dog moves in the other 

 direction. In other words, in whichever 

 direction the light travels, there, also. 



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