166 THE AGE OP ELECTRICITY. 



before, on the IGtli Brumaire of the year 10, after atteiidiug the sitting 

 of tlie institute at wliicli Volta's jiaper on the pile was read, he was 

 struck with the idea that it woukl be a credit to France to open a con- 

 test to which all the scientists from all countries should be invited, and 

 to award an extraordinary prize " to the most valuable writing on this 

 branch of physics which seemed to open the way for great discoveries." 



Progress in science is made by starts, when a felicitous experiment 

 or a stroke of genius brings a change in its confines. It took over 

 twenty years after Volta to find whether any perceptible phenomenon 

 takes place in the copper conductor which connects the two poles in 

 the pile. The discovery of Oersted and the immortal investigations of 

 Ampere established a relation between electricity and magnetism ; iron 

 was magnetized by means of currents and electrical telegraphy was the 

 result. 



But what a number of questions then confronted our minds. As long 

 as the i)henomena remained independent of one another, they could be 

 explained by special theories applying to each one of them. It was the 

 day of fluids. After the caloric fluid, it cost no greater ettort to imagine 

 the two electric fluids and the two magnetic fluids, to say nothing of 

 the neutral fluids required to connect them, and the ether with which 

 the universe was filled to serve as a medium of transmission of light. 

 No true philosophy can be based on such a multiplicity of independent 

 entities, for phenomena are not confined in distinct provinces with their 

 immediate causes. Ampere had already pointed out that it would 

 undoubtedly be necessary to turn to the intervention of the fluid that 

 pervades all si)ace in order to explain the forces that operate between 

 conductors carrying electric currents. 



The agent itself remains a mystery, a title that electricity enjoys by 

 privilege, as it were. Yet we must admit without looking back to the 

 origin of all things, that science is everywhere face to face with myste- 

 ries — universal gravitation, heat, constitution of bodies, light, electric- 

 ity, magmetism, life, — 



While habit impels us to accept such of these as come under the 

 more direct observation of our senses, they remain none the less inex- 

 plicable, and we must confine ourselves to a study of experimental laws, 

 more or less connected by other laws of a more general character, with- 

 out any possibility of penetrating the intimate structure of the universe. 

 One of the great minds of our age, in whose presence wonder was 

 expressed at the inexplicability of certain phenomena, remarked with 

 profound neaning: "Tell me what electricity is and I will tell you all 

 the rest." 



After Oersted and Ampere, a great step remained to be made. 

 "When it is seen," said Fresnel in 1820, "that an electric current 

 running through a metallic helix wound around a steel cylinder mag- 

 netizes the latter, it seems natural to try whether a magnetized bar 

 is not capable of producing a voltaic current in the surrounding 



