Applications of Electricity; 



233 



Fuses are installed in house circuits to protect against the 

 'dangers of crossed wires. A fuse consists of a short piece of 

 wire with a comparatively low melting point, usually enclosed in 

 a protecting cylinder or plug 1 for convenience in inserting into the 

 circuit. If the current becomes too great for safety the fuse 

 melts and breaks the circuit, shutting off the electricity. 



X-rays. X-rays were discovered by a German physicist, 

 named Rontgen, near the close of the 19th century. In the 



X-RAY PHOTOGRAPH OF AN ELBOW 



course of his experiments, while passing electric charges through 

 a vacuum tube, he observed that a certain kind of radiation was 

 given off which would pass through such opaque objects as wood, 

 pasteboard and flesh. As the nature of these rays was unknown 

 to him, he called them X-rays. These rays affect a photographic 

 plate somewhat as sunlight does. When a photographic plate of 

 sufficient sensitiveness is placed against any part of the body, 

 such as the arm, and X-rays are passed through that part, they 



