488 THE INTELLECTUAL RISE IN ELECTRICITY. 



Apart from the discoveries in which they resulted, the 

 researches of both Gray and Dufay are remarkable for their 

 inductive character and the absence of dogmatizing on the 

 nature and cause of electricity. Concerning the last, 

 opinions were undergoing radical change. Shortly after 

 Hauksbee's experiments were published, Dr. s'Gravesande, 

 Professor of Mathematics at Leyden, issued one of the 

 earliest, if not the earliest, didactic work in which elec- 

 tricity is treated as a branch of physics, and there gives it 

 as his ultimate conclusion, based on preceding experi- 

 ments, that there is an atmosphere excited in rubbed glass 

 by friction, which attracts and repels light bodies, and also 

 that out of the glass, fire is forced ; but he does not regard 

 either the atmosphere or the fire as electricity, which he de- 

 fines as "that property of bodies by which (when they are 

 heated by attrition) they attract and repel lighter bodies at 

 a sensible distance." 



The experiments of Gray and Dufay showed the light 

 and the fire to be as much an electrical phenomenon as the 

 attraction and repulsion; but Dufay's discovery of the dual 

 nature of electricity had undermined the old conception of 

 material emanations, while definitely establishing no new 

 theory in its place. 



After the death of Dufay appears Dr. Desaguiliers, a 

 man of considerable prominence in the Royal Society. He 

 had never found it expedient to discourse about electrical 

 matters so long as either Gray, whom he seems to have 

 disliked, or Dufay survived; but afterwards he contributes 

 many papers to the Philosophical Transactions, in which 

 he collects a great mass of experiments, chiefly in the na- 

 ture of cumulative evidence. He invented the term "elec- 

 trics per se," which, for a long time afterwards, was used 

 to designate those bodies which could be made electric by 

 rubbing them, although it was nothing but a polyglot 

 translation of Dufay's term "electriques par etix-memes." 

 He also first used the word *' conductor," applying it to 

 the string over which the electricity passes, and also was 



