2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. y6 



MACHINES GENERATING ELECTRICITY BY FRICTION 



Otto \o\-\ Gnericke was mayor of the city of Magdeburg as well as 

 a philosopher. About 1650 he made a machine consisting of a ball 

 of sulphur mounted on a shaft which could be rotated. Electricity 

 was generated when the hand was pressed against the globe as it 

 rotated. He also discovered that electricity could be conducted away 

 from the globe by a chain and would appear at the other end of the 

 chain. Yon Guericke also invented the vacuum air pump. In 1709, 

 Francis Hawksbee, an Englishman, made a similar machine, using a 



Otto Von Guericke's Electric Machine, 1650. 



A ball of sulphur was rotated, electricity being generated when it 

 rubbed against the hand. 



hollow glass globe which could be exhausted. The exhausted globe 

 when rotated at high speed and rubbed by hand would produce a glow- 

 ing light. This " electric light " as it was called, created great excite- 

 ment when it was shown before the Royal Society, a gathering of 

 scientists, in London. 



Stephen Gray, twenty years later, showed the Royal Society that 

 electricity could be conducted about a thousand feet by a hemp thread, 

 supported by silk threads. If metal supports were used, this could not 

 be done. Charles du Eay, a Frenchman, repeated Gray's experiments, 

 and showed in 1733 that the substances which were insulators, and 



