XIV 



PROGRESS IN ELECTRICITY FROM GILBERT 

 AND VON GUERICKE TO FRANKLIN 



WE have seen how Gilbert, by his experiments 

 with magnets, gave an impetus to the study of 

 magnetism and electricity. Gilbert himself demon- 

 strated some facts and advanced some theories, but 

 the system of general laws was to come later. To this 

 end the discovery of electrical repulsion, as well as 

 attraction, by Von Guericke, with his sulphur ball, 

 was a step forward; but something like a century 

 passed after Gilbert's beginning before anything of 

 much importance was done in the field of electricity. 

 In 1705, however, Francis Hauksbee began a series 

 of experiments that resulted in some startling demon- 

 strations. For many years it had been observed that 

 a peculiar light was seen sometimes in the mercurial 

 barometer, but Hauksbee and the other scientific in- 

 vestigators supposed the radiance to be due to the 

 mercury in a vacuum, brought about, perhaps, by 

 some agitation. That this light might have any 

 connection with electricity did not, at first, occur to 

 Hauksbee any more than it had to his predecessors. 

 The problem that interested him was whether the vacu- 

 um in the tube of the barometer was essential to the 

 light; and in experimenting to determine this, he in- 

 vented his "mercurial fountain." Having exhausted 



259 



