220 THE DEVELOPMENT OF ELECTRICAL SCIENCE. 



of other crystals. iEpinus made experiments in other branches of 

 electricity, but he is chiefly noted for his ingenious single-fluid theory 

 of electricity. 



Between the years 1770 and 1780 the electrical organs of the torpedo 

 were one of the principal topics of discussion. The experiments of 

 Walsh aud Ingenhousz were the first to definitely settle the character 

 of the peculiar power of the fish. 



The experiments of Cavendish belong to this period and were remark- 

 able as being quantitative in their character. Considering the means 

 at his command, the measurements made by this experimenter of the 

 relative conducting powers of various substances must always excite 

 admiration. Cavendish also proved the composition of water by caus- 

 ing different proportions of oxygen and hydrogen to unite by means of 

 the electric spark. 



We now come to the classical experiments of Coulomb, who estab- 

 lished the law of the variation of the electric force with distance to be 

 that of the inverse square, a law which had previously been inferred 

 from experiments on spheres by Dr. Robinson, who, however, 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 

 developed shortly afterwards by Laplace, Biot, and Poisson, the work 

 of the latter being particularly important. 



Toward the end of the eighteenth century were made the important 

 researches of Laplace, Lavoisier, and Volta, and of Sausure on 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. 



To the eighteenth century, also, we must assign the discovery of 

 galvanic electricity, as the famous frog experiments were made in 

 1790. Practically no development was made, however, until Volta's 

 work attracted the attention of the scientific world. 



At the beginning of the nineteenth century, then, we find the 

 subjects of greatest interest were the discoveries of Volta and the 

 invention of the voltaic pile. There followed almost immediately the 

 discovery by Nicholson and Carlisle of the decomposition of water by 

 the voltaic current. This discovery was followed a few years later by 

 those of Sir Humphry Davy on the decomposition 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 interrelation between electricity and magnetism? 

 was now the query. The first positive answer sftems to have been 



