TEE PHYSICAL LABORATORY 113 



electricity was embraced in the knowledge obtained by the Frenchman 

 Coulomb regarding the law of force with which electricity at rest upon 

 conducting bodies attracts and repels other electricity. Nothing was 

 known of the phenomena of electricity in motion, flowing, as we say, in 

 a current. It was not until 1827 that the law stating the dependence 

 of the strength of the current on the driving-power of the battery caus- 

 ing it was discovered by the German Ohm. But a fundamental dis- 

 covery was made in 1820 by the Dane Oersted when he found that the 

 current in a wire would act upon a magnet anywhere in its vicinity, or 

 would produce what we now call a magnetic field. Upon this discovery 

 depends the possibility of all our telegraphs, for which the current was 

 soon utilized. But a more powerful intellect than that of Oersted, 

 namely that of the Frenchman Ampere, inspired by Oersted's discovery 

 that a current acted like a magnet, reasoned that in that case two cur- 

 rents would exert magnetic forces upon each other, and in a wonderful 

 series of researches determined the mathematical laws of these mutual 

 actions of currents in the most complete manner. When we see the 

 primitive apparatus with which Ampere made these brilliant discoveries, 

 we are led to have the most profound admiration for his brilliant ex- 

 perimental and mathematical genius, and we may secretly wonder 

 whether we have not laid too much emphasis to-day on fine laboratories 

 and equipments. The next commanding genius that appears on the 

 scene, whose work is more important than any of those yet mentioned, 

 is Michael Faraday, professor at the Royal Institution, a laboratory for 

 research and popular lectures, founded by our own countryman who 

 later became Count Rumford, but made forever famous by the dis- 

 coveries there made during a long term of years by Faraday. Those 

 who have visited the laboratories at the Royal Institution will be sur- 

 prised at the total lack at that time of all the conveniences that we to- 

 day expect, but Faraday was no doubt perfectly satisfied with it. To- 

 day electric lighting and supply of current in a laboratory is a common- 

 place — then there was not even gas, and all currents had to be made by 

 batteries laboriously filled with chemicals for each time of use. There 

 was no insulated wire, and Faraday had to wind his own with thread or 

 ribbon. Among the greatest triumphs of Faraday was his discovery of 

 the converse of the production of magnetism by electrical current; I 

 mean the production of current by magnetism. After long attempts, 

 he found that if a magnet was moved into, out of, or in the neighbor- 

 hood of a coil of wire forming a complete circuit, then a current of 

 electricity was induced, as he put it, in the coil during the motion of 

 the magnet. This is the germ of our dynamo-electric machines which 

 to-day supply all the current for our light, power and electric traction. 

 Could Faraday have seen the huge dynamos of ten thousand horse- 

 power each that convey the power of Niagara Falls to regions a hun- 



