9 



CHAPTER I. 

 DISCOVERY OF LAWS OF ELECTRIC PHENOMENA. 



WE have already seen what was the state of 

 this branch of knowledge at the beginning 

 of the seventeenth century, and the advances made 

 by Gilbert. We must now notice the additions 

 which it subsequently received, and especially those 

 which led to the discovery of general laws, and the 

 establishment of the theory; events of this kind 

 being those of which we have more peculiarly to 

 trace the conditions and causes. Among the facts 

 which we have thus especially to attend to, are the 

 electric attractions of small bodies by amber and 

 other substances when rubbed. Boyle, who re- 

 peated and extended the experiments of Gilbert, 

 does not appear to have arrived at any new general 

 notions; but Otto Guericke of Magdeburg, about 

 the same time, made a very material step, by dis- 

 covering that there was an electric force of repul- 

 sion as well as of attraction. He found that when 

 a globe of sulphur had attracted a feather, it after- 

 wards repelled it, till the feather had been in contact 

 with some other body. This, when verified under 

 a due generality of circumstances, forms a capital 

 fact in our present subject. Hawkesbee, who wrote 

 in 1709 (Physico-Mechanical Experiments,} also 



