FREE INSTITUTE OF SCIENCE 



ETHER WAVES AND THE MESSAGES THEY BRING 



73 



which were able to affect a photographic plate through glass, paper, flesh, and 

 even thin layers of metals. This discovery created a great stir among scien- 

 tists, and before long many men were working on the subject. It is not my 

 purpose to trace the development of our early knowledge of these rays, nor 

 their appHcation to photography and medicine. I do, however, wish to demon- 

 strate their power of penetration. The waves themselves are much too short 

 to be detected by the eye, but, allowed to fall on certain substances, such as 

 platinum barium cyanid, they produce a fluorescence which can be seen. Now, 

 if any object be passed between the tube and the screen, they will or will not 

 reach the screen, depending upon whether or not they are able to penetrate the 

 interposed substance. A small body which they cannot penetrate will cut 



d <. 





U//raP1o/d: 



l^/sii>}^. 



f/^f/V' r-eaf. 



Lhk/70^/7, 



Hert^-U6^-!S^s. 



N ^ 



^ 



I 



Fig- S- — Diagram, not drawn to scale, of spectrum, including all known ether waves. Wave lengths 



are given in Angstrom units. 



them off from a part of the screen and that part of the screen will not fluoresce. 

 Thus the body is seen, in effect, by its shadow on the screen. If the screen 

 be replaced by a photographic plate, a picture may be made of the shadow. 



For about seventeen years these rays were used and studied without know- 

 ing their exact nature. In 191 2 Dr. Max Laue, of Munich, identified them as 

 ether waves of very short wave length. His method will be clear if we refer 

 for a moment to the principle of diffraction in Kght. If a beam of light be 

 passed through a grating made by ruHng on glass many fine parallel lines 

 equally spaced, a spectrum is produced which is for all purposes like that pro- 

 duced by the prism. In order to be effective the grating must have in general 

 lines so close together that the distances between them are of the same order of 



