84 THE NEW KNOWLEDGE. 



actual plate, which is here produced (Fig. 20) leaves no muddy 

 obscurity for the reader. Upon the plate are imprinted the 



Fig. 20. The result of Niewenglowski 's Experiment. 



square of glass and the round section of the clock-glass cover. 

 The rays had, necessarily, to pass straight through the alumi- 

 num cover-slide to print them there. It was thus, then, 

 that the question was asked of Nature, "Does this sub- 

 stance, this calcium sulphide, emit rays which will pene- 

 trate glass and metal and affect a photographic plate?" 

 And Nature answered in her legible signature, "This sub- 

 stance will." Are these rays light? The answer is upon the 

 same plate. It is affirmative. If you examine the im- 

 print of the square of glass upon this plate, you will notice 

 that it is bordered by a perfectly white line which has been 

 left untouched by the rays. This can only be accounted for 

 by supposing that they were bent, or refracted, on passing 

 through the edges of the glass into the air. Now rays that 

 are made up of particles, or corpuscles such as we have 

 studied in Part III, cannot be refracted in the slightest de- 

 gree. Light rays always are, and must be, from their very 

 nature, as wave motions. Niewenglowski, therefore, dis- 

 covered penetrating rays of light capable of passing through 

 a sheet of metal, a substance which anybody would consider 



