VON GUERICKE'S DISCOVERIES. 403 



Such was the conception which Guericke sought to es- 

 tablish. The effort resulted in the discovery of electrical 

 conduction, of electrical polarity, of the transmission of 

 electrification over an elongated conductor, of electric 

 light, of sound produced by electricity, of the discharging 

 capacity of points, of the dissipation of charge by hot air, 

 and of the vibration of a freely- movable body due to its 

 charge and discharge; the first recognition of electrical 

 repulsion as such, a direct suggestion of the identity of 

 electrical attraction and gravity, and the construction and 

 successful use of the first machine for the production of 

 electricity. 1 



And all these accomplishments remained practically un- 

 noticed until the days of Dufay. Well might that gene- 

 rous discoverer detect in them the cause of subsequent 

 progress, and express his astonishment that they had re- 

 mained so long forgotten. 



1 On peut voir dans le recit abre"ge" de ces experiences, la base et la 

 principe de toutes celles qui ont e"te faites depuis avec le tube et le globe 

 de verre: et on ne peut s'empecher d'etre surpris quelles ayant demeure' 

 si longtemps dans 1'oubli, ou du moins qu'on ne se soit pas avise" de les 

 repeter et de tacher de les porter plus loin. Mem. de 1'Acad. Roy. des 

 Sci., 1733, 25. 



