62 



TRANSACTIONS OF WAGNER 



ETHER WAVES AND THE MESSAGES THEY BRING 



to the wave lengths, and vary from perhaps a few thousand per second to hun- 

 dreds of trillions per second. Since light waves are the best known of all of 

 these, let us begin our study with them and then, as time permits, take up those 

 less well known. 



It is commonly known that a beam of white light is composed of trains of 

 waves of differing wave lengths, and that if the beam is passed through a prism 

 and bent considerably out of a straight path, the waves of different lengths 

 will be separated, since the short waves are bent more than the long ones. 

 You can see on the screen (Fig. i, ^) the effect of thus separating out the dif- 



R 



& 



n 



O Y 



B 



V 



fl B C D Eh F 



HH' 



Fig. I. — A, Continuous spectrum; B, solar spectrum, showing dark lines; C, bright-line spectrum 



of sodium vapor. 



ferent wave lengths. The red represents the longest, the violet, the shortest, 

 visible waves in the beam. Those of intermediate length lie on the screen be- 

 tween the red and the violet, orange, yellow, green, and blue. Now by several 

 methods, depending on the principle of interference, the length of the waves 

 producing these various colors can be accurately measured. The deepest 



o o 



red ones are about 7800 Angstrom units, the shortest violet about 3800 Ang- 

 strom units in length. Ether waves lying within these limits are the only ones 

 visible to the human eye. Others do not reveal themselves to our unaided 

 senses, but must be detected by some other means. We shall speak of these 

 others later; there are many of them. For the present, however, I wish to 

 consider the visible waves and a number of interesting facts they have revealed 

 to us. 



The best method of studying these dispersed rays or spectra, as they are 



