364 



SCIENCE. 



[N. S. Vol. VII. No. 168. 



ing the means at his command, the meas- 

 urements made by this experimenter of the 

 relative conducting powers of various sub- 

 stances must always excite admiration. 

 Cavendish also proved the composition of 

 water by causing different proportions of 

 oxygen and hydrogen to unite by means of 

 the electric spark. 



We now come to the classical experiments 

 of Coulomb, who established the law of the 

 variation of the electric force with distance 

 to be that of the inverse square, a law which 

 had previouslj^ been inferred from experi- 

 ments on spheres by Dr. Eobinson,who, how- 

 ever, did not publish his results. Coulomb 

 made an elaborate series of experiments on 

 the distribution of electricity over charged 

 conductors as influenced by shape and the 

 proximity of other charged bodies. His 

 theoretical and experimental work formed 

 the basis of the mathematical theory as de- 

 veloped shortly afterwards by Laplace, Biot 

 and Poisson, the work of the latter being 

 particularly important. 



Toward the end of the ISth centurj^ were 

 made the important researches of Laplace, 

 Lavoisier and Volta, and of Sausure in the 

 electricity produced by evaporation and 

 combustion. This is a subject destined to 

 figure prominently again in the future, and 

 in its rise there is in all probability involved 

 the rapid decline in the importance of the 

 steam engine. I should not be surprised if 

 many of those present should live to see 

 the steam engine practically a thing of the 

 past. 



In the ISth century also we must assign 

 the discovery of Galvanic electricity, as the 

 famous frog experiments were made in 1790. 

 Practically no development was made, how- 

 ever, until Volta's work attracted the at- 

 tention of the scientific world. 



At the beginning of the 19th Century, 

 then, we find the subjects of greatest inter- 

 est were the discoveries of Volta and the 

 invention of the voltaic pile. There fol- 



lowed almost immediately the discovery 

 by Nicholson and Carlisle of the decomposi- 

 tion of water by the voltaic current. This 

 discovery was followed a few years later by 

 those of Sir Humphry Davy on the decom- 

 position of the alkalies and the separation 

 of metallic sodium and potassium. Thus 

 the subject of electrolysis was fairly 

 launched, and what it has grown to be we 

 will see later. 



Can there be some inter-relation between 

 electricity and magnetism was now the 

 query ? The first positive answer seems to 

 have been given by Romagnesi in a work 

 published in 1805, but little or no notice 

 appears to have been taken of this. Cer- 

 tainly no progress was made in the subject 

 till 1820, when Oersted made his famous 

 experiment before his class. By that ex- 

 periment he proved that a wire carrying an 

 electric current will, when properly placed, 

 deflect a magnetic needle. The subject was 

 almost immediately taken up by Ampere, 

 and in a few months many of the impor- 

 tant consequences which Oersted's discovery 

 involved were developed. Ampere's work 

 on the action of currents on currents and 

 on magnets is classical and is still treated 

 as part of the fundamental basis for the 

 theory of electrodjmamics. An account of 

 his work may, therefore, be found in almost 

 any of the numerous text-books on electric- 

 ity. The conclusions reached by Ampere 

 were confirmed by Weber by a series of 

 much more refined experiments. To Weber 

 also we owe improvements in galvanom- 

 eters. The same year marks the discov- 

 eries by Arago that a current can not only 

 deflect a magnet, but that it is capable of 

 producing one by magnetizing steel needles. 



The further discovery was made four 

 years later by Sturgeon that soft iron al- 

 though incapable of making a strong per- 

 manent magnet is yet much more suscepti- 

 ble to temporary magnetization by the 

 electric current. Arago also made about 



