56 "nature's flfefraclee. 



when it reaches a sufficiently high rate throws 

 the ether into a vibratory motion that we calJ 

 light. However, this vibratory motion of the 

 ether is set up long before it reaches the lumi- 

 nous stage ; in other words, there are dark ray? 

 of the ether. We find that the electro-atomic 

 motions of a conductor have the power to im" 

 press themselves upon the ether. 



Let us try another experiment to show that 

 this is the case, not only, but that the im- 

 pressed ether can transfer these impressions to 

 still another conductor. Suppose we stretch 

 two parallel wires for, say, half a mile, or any 

 distance, only a few feet apart, and make of. 

 each a complete circuit by rounding the end 

 of the course and returning the wire to tho 

 starting point (as shown in Fig. 1). Put in 



Fl g'. I 



A 5 



c 



PRIMARY LINE 



c 



A is the primary line; a, the hattery; 6. the key. B if 

 the secondary line in which is placed the galvanometer c. 



one of these circuits a battery, and a circuit- 

 breaker (a common telegraph-key), and in the 

 other circuit a galvanometer (an instrument 

 for detecting the presence and measuring the 

 intensity of a galvanic current, by means of a 



