CHAPTER X 



ELECTRICAL INVENTIONS 



Invention breeds invention. EMERSON 



Now all these discoveries, besides being interesting in them- 

 selves, led to a number of practical inventions of great impor- 

 tance. It has repeatedly been true that men have sought out 

 nature's secrets to satisfy their curiosity without any thought 

 of their immediate use, only to find in. later years that the facts 

 discovered were of immense value to man in increasing his 

 happiness and well-being. So we support scientific investiga- 

 tions of all sorts in the belief that the facts discovered will some 

 day be of use, even if at the present they cannot be turned to 

 commercial account. They satisfy our longing to understand 

 the universe about us, and this mental satisfaction is really quite 

 as important as physical comfort and luxury. 



The first of these great practical inventions in electricity was 

 the telegraph. Two types of telegraph instruments were invented 

 and put into general use. Wheatstone and Cook of England 

 in 1837 patented an instrument that depended on the facts that 

 a magnetic needle is deflected when an electric current is sent 

 through a wire that passes over and under it, and that the direc- 

 tion of the deflection depends upon the direction of the current. 

 The sending instrument consisted of a device for making and 

 breaking the current and for reversing its direction at will. The 

 receiving instrument was simply a magnetic needle mounted in 

 a coil in such a way as to be free to swing in a plane at right 

 angles to the plane of the coil. Then, by previously agreeing 

 upon a set of signals to indicate the letters of the alphabet, it 

 was perfectly possible to send a message. Thus, one swing of 

 the north end of the needle to the left meant Cj one to the left 



