Page:Popular Science Monthly Volume 88.djvu/454

 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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