518 TRANSACTIONS OF THE 



added but little to Gilbert's discoveries. About 1670 Boyle en- 

 gaged in the study of it, and said that the fluid passed through 

 vacuum. (Now denied.) Otto Guericke, a cotemporary of 

 Boyle's, used a globe of sulphur, whirled on its axis in the same 

 way with our modern glass globes, and by that sulphurous globe 

 obtained vastly more electricity than had ever before been pro- 

 duced. Otto discovered electric repulsion, and the fact that a 

 feather repelled from an electric always presented the same face 

 to it, as the moon does to the earth. 



In February, 1729, Stephen Gray discovered the distinction 

 between conductors and non-conductors of electricity. Soon after 

 Gray, Du Fay discovered positive and negative electricity, called 

 vitreous and resinous. The capital discovery of the Ley den 

 phial was accidentally made in 1745. Then the study 'began 

 to be general. The discoverer was Van Kleist, dean of the cathe- 

 dral in Camin. The name of Ley den phial was given by Mr. 

 Cunseus, a native of Leyden, who made many experiments with 

 Kleist's jar. Cunseus happened to hold his glass vessel in one 

 hand, and witH the other trying to disengage the conductor, in an 

 experiment to charge water with electricity, was surprised by a 

 » sudden shock in his arms and breast. The philosophers were 

 greatly excited by this, and Muschenbrceck, repeating the experi- 

 ment, told Reaumur that he felt struck in his arms, shoulder, and 

 breast, so that he lost his breath, was two days before he recov- 

 ered from the blow and the terror, and that he would not take 

 another shock for the whole kingdom of France. Next came 

 Franklin, who in 1750 first " eripuit ccelo fulmen," &c. His 

 theory was demonstrated in 1752, on the 10th of May, during a 

 thunder storm, by Messrs. Dalibard and Delor, at Marly la ville, 

 five or six leagues from Paris, by a rod. Dr. Franklin tried the 

 experiment about a month afterwards in Philadelphia, with a kite 

 made of a silk handkerchief and two cross sticks. Afraid of 

 ridicule, he told nobody but his son what he was doing. He got 

 under a shed to shelter them from the storm. It was some time 

 after he got his kite up before he found any results. He at* last 

 succeeded. After that he erected an iron rod, insulated, and 

 from that drew the real lightning down, and with it repeated all 



