A HUNDRED YEARS OF CHEMISTRY. 63 



The rarest metals can now be separated from their oxides with per- 

 fect ease, and new compounds, obtainable in no other way, the 

 furnace has placed at our disposal. This field of research is now 

 barely opened; from it the twentieth century should gather a rich 

 harvest. 



With electricity also chemistry is nearly allied, and along some 

 lines the two branches of science have been curiously intertwined. 

 Like the other- physical forces, electricity may either provoke 

 or undo combination, and, like heat, it may itself be generated as 

 a product of chemical action. The voltaic pile and the galvanic 

 battery owe their currents to chemical change, and it is only since 

 the middle of the century that any other source of electric energy 

 has become available for practical purposes. It is not surprising, 

 therefore, that many thinkers should have sought to identify chem- 

 ical and electric force, the two have so much in common. It was 

 with the galvanic current that Davy decomposed the alkalies, and 

 since his day other electro-chemical decompositions have been stud- 

 ied in great number, to the development of important industries. 

 To the action of the current upon metallic solutions we owe the 

 electrotype and all our processes for electroplating, and these 

 represent only the beginnings of usefulness. Even now, almost 

 daily, advances are being made in the practical applications of 

 electrolysis, and the forward movement is likely to continue 

 throughout the coming century. From the curiously reversible 

 chemical reactions of the secondary battery the automobile derives 

 its power, and here again we find a field for invention so large that 

 its limits are beyond our sight. From every peak that science can 

 scale new ranges come into view. The solution of one problem 

 always creates another, and this fact gives to scientific investigation 

 its chief interest. We gain, only to see that more gain is possible ; 

 the opportunity for advance is infinite. Forever and ever thought 

 can reach out into the unknown, and never need to weep because 

 there are no more worlds to conquer. 



It was the study of electro-chemical changes which led Ber- 

 zelius to his electro-chemical theory of combination, and then to 

 the dualistic theory, which has already been mentioned. In or 

 about the year 1832, when the Berzelian doctrines were at the 

 summit of their fame, Faraday showed that the chemical power of 

 a current was directly proportioned to the quantity of electricity 

 which passed, and this led him to believe that chemical affinity and 

 electric energy were identical. Electrolysis, the electrical decom- 

 position of compounds in solution, was a special object of his atten- 

 tion, and by quantitative methods he found that the changes pro- 

 duced could be stated in terms of chemical equivalents or combin- 



