STUDIES IN ATMOSPHERIC ELECTRICITY. 7 



passing down against them, was received by a plate on the insulator. 

 The electrometer showed negative electrifications. From these ex- 

 periments we may conclude that the above named objects become 

 positively, and sand negatively electrified by their nuUual friction. 



Experiment II. — The friction of water particles with leaves, 

 twigs, w^ood, etc. These objects were placed upon the insulator, and 

 to them was directed a jet of steam from tlie finely drawn out end oï 

 a horizontal glass tube 1.5 m. long, whose other end was bent down 

 into a fiask of boilino- water. The electrometer showed sliü'ht neo-ative 

 electrifications of these objects, except in one case, namely dry ice, 

 which shoAved itself positively electrified. Though this group of 

 experiments gave results with less degree of certainty than the rest, 

 I contented myself with them ; for exactly the same results had been 

 already obtained by many investigators. For instance, Faraday^ ^ 

 proved in his fiunous experiments conducted for the explanation of 

 Armstrong's hydroelectric machine, that water becomes positively 

 electrified by friction with many substances, for instance, ivorv, 

 quartz, glass, etc.; but becomes negatively electrified by friction with 

 dry ice. Elster,-* in investigating the electromotive force excited in 

 a stream of water, showed that the electrificatiori took place solely 

 where the water was in contact with solids such as mica, airate, 

 caoutchouc, wax, glass, porcelain, etc., and where the water mass 

 experienced friction, and that the electrification was such that water 

 acquired positive electricity with regard to these substances. Again 

 Sohncke^^ proved that ice became positively electrified by friction wdth 

 water, and also that ice was positive against all the substances he 

 tried, e.g. steel, brass, glass, dust in the air, etc. 



1 ) Faraday, Experimental Researches, II. p. 106. 



2) Elster, Wied. Ann. 6, P- 553. 1879. 



3) Sohncke, Wled. Ann. 23. P- 550. 188Ö. 



