DISCOVERIES IN THE CELESTIAL SPACES. 727 



se electrice congregatur et cohseret; for the tendency of the 

 electric action is to produce the cohesive accumulation of 

 matter (motus electricus est motus coacervationis materia3)." 

 In these, obscure axioms we trace the recognition of terres- 

 trial electricity the expression of a force which, like mag- 

 netism, appertains as such to matter. As yet we meet with 

 no allusions to repulsion, or the difference between insulators 

 and conductors. 



Otto von Guerike, the ingenious inventor of the air- 

 pump, was the first who observed anything more than mere 

 phenomena of attraction. In his experiments with a rubbed 

 piece of sulphur, he recognised the phenomena of repulsion, 

 which subsequently led to the establishment of the laws of 

 the sphere of action, and of the distribution of electricity. 

 He heard the first sound, and saw the first light in artificially 

 produced electricity. In an experiment instituted by Newton 

 in 1675, the first traces of the electric charge in a rubbed plate 

 of glass were seen.* 1 We have here only sought the earliest 

 germs of electric knowledge, which, in its great and singu- 

 larly retarded development, has not only become one of the 

 most important branches of meteorology, but has also thrown 

 much light on the internal action of terrestrial forces, since 

 magnestism has been recognised as one of the simplest forms 

 under which electricity is manifested. 



Although Wall in 1708, Stephen Gray in 1734, and Nollet, 

 conjectured the identity of friction-electricity and of lightning, 

 it was first proved with empirical certainty in the middle 

 of the eighteenth century by the successful efforts of the cele- 

 brated Benjamin Franklin. From this period the electric pro- 

 cess passed from the domain of speculative physics into that of 

 cosmical contemplation, from the recesses of the study to 

 the freedom of nature. The doctrine of electricity, like that 

 of optics and of magnetism, experienced long periods of 

 extremely tardy development, until in these three sciences 

 the labours of Franklin and Volta, of Thomas Young and 

 Mains, of Oersted and of Faraday, roused their cotempo- 

 raries to an admirable degree of activity. Such are the 

 alternations of slumber and of suddenly-awakened activity 

 that appertain to the progress of human knowledge. 



But if, as we have already shown, the relations of tem- 

 * Brewster, Life of Newton, p. 307. 



