The Evolution of Electric and Magnetic Physics. 161 



is now the basis of all international measurements, electrical 

 as well as scientific. This system is like a universal lan- 

 guage, which enables observers in one part of the world to 

 make their discoveries intelligible in other countries. This 

 is now the base for all international scientific measurements. 

 The advantage that science has gained by this co-operative 

 effort has been very great, and engineering has been simi- 

 larly benefited. ^ 



The great utilitarian progress made since that time has 

 been in the invention of the telephone, the electric light, 

 and machinery for the transmission of electric power all 

 the outcome of electro-magnetic induction. The first 

 electric telephone was made by Reis in 1868, but it was 

 only applicable to the reproduction of musical sounds at a 

 distance, its articulation being too restricted to convey 

 speech successfully. The first practical speaking telephone 

 was made by Alexander Graham Bell in 1876. It is now in 

 use all over the civilized world, and many pages could be 

 written upon its development alone. 



The carbon arc light of Davy, while very useful for many 

 purposes calling for intense illumination, was very costly 

 while sustained by galvanic batteries. To produce it more 

 conveniently and cheaply, the dynamo machine was slowly 

 improved. The dynamo as it existed in the year of Fara- 

 day's discovery was little more than a scientific toy; at 

 the present time dynamos are in operation that singly 

 transform the mechanical power of a steam-engine into 

 electrical energy to the working value of five thousand 

 horses. 



The study of the arc light and its capabilities led to the 

 search for an incandescent lamp. In the hands of Edison 

 the incandescent lamp became not only a possibility, but a 

 practical success. 



The most important phases of the subject at the present 

 time may thus be summed up : 



1. In electro-magnetic science the great achievement since 

 Faraday's time has been the determination of the fact that 

 all electricity flows, or tends to flow, in closed curves or cir- 

 cuits, so that we have the electrostatic circuit, the galvanic 

 circuit, and the magnetic circuit, each resembling, as it were, 

 an endless chain or a bundle of endless chains ; and the laws 

 which control these three different types of circuit show 

 wonderful analogies. 



2. The due appreciation of the influence of the ether and 



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