WHAT IS ELECTRICITY ? 83 



regard to electricity, we seldom reflect that gravitation is as great 

 a mystery as electrical attraction. What is this force which acts 

 instantly through space, and which holds our entire solar system 

 together? We know only its simple law — that it attracts bodies 

 directly as their masses and inversely as the square of their distance ; 

 but we do not know what relation it bears to electrical force or 

 magnetic force. Here is a field in which we are to push back our 

 boundary of electrical knowledge. I will not call it electrical knowl- 

 edge, but rather our knowledge of the great doctrine of the conserva- 

 tion of energy. What is the relation between electricity, magnetism, 

 and gravitation, and what we call the chemical force of attraction ? 

 It seems to me that this is the question which we must strive to an- 

 swer ; but, when this question is answered, shall we not be as far as 

 ever from the answer to the question, " What is electricity ? " 



The question of the connection between electricity and gravitation 

 dwelt much in Faraday's thoughts. It is interesting to recall the ex- 

 periments which he instituted to discover if there is any connection 

 between these great manifestations of force. In his first experiment 

 he suspended vertically an electro-magnet, which was connected with 

 a delicate galvanometer, and let various non-magnetic bodies, such as 

 brass bodies, pieces of stone and crystals, fall through the center of 

 this electro-magnet, thinking that there might possibly be a reaction 

 from the influence of gravitating force on the falling body which 

 would be manifested as an electrical current. He did not, however, 

 obtain the slightest electrical disturbance which might not have been 

 caused by simple electrical induction. He then arranged a somewhat 

 complicated piece of apparatus by means of which a body could be 

 moved alternately with the direction of gravitation and against it, 

 and the terminals of a galvanometer were so connected that the inter- 

 mittent effects, if they existed, could be integrated or summed up. 

 He failed, however, to find the slightest relation between gravitation 

 and electricity, and he closes his account of his experiments with these 

 words : " Here end my trials for the present. The results are negative. 

 They do not shake my strong feeling of the existence of a relation 

 between gravity and electricity, though they give no proof that such 

 a relation exists." 



Since Faraday's time no connection or relation has been found ex- 

 cept in the similarity of the law of inverse squares. I have often re- 

 flected upon these experiments of Faraday, and have asked myself, 

 Was the direction in which he experimented the true direction to look 

 for a possible relation ; and can not the refined instruments and 

 methods of the electrical science of the present aid us in more prom- 

 ising lines of research ? Should we not expect that, when two balls 

 of copper, for instance, are suddenly removed from each other, a dif- 

 ference of electrical potential should manifest itself, and that the 

 electrical force thus developed should be opposed to our endeavor to 



