ART. 7.— Y. HOMMA: 



an experiiiieiit of ]\Ia.scnrt'.s, avIio observed (1878) that the evaporation 

 took place more rapidly from an electrified li(piid than from a 

 neutral one. 



Edlund's theory'^ of imipolar induction considers the earth as^ 

 a rotating conducting sheath, Avithin Avhich a magnet is situated. 

 The induction, as he calculates, causes positive electricity to ac- 

 cumulate in tlie upper atmosphere, which is the origin of atuKjspheric 

 electricity. 



Sohncke^^ ascribed the cause of atmospheric electricity to the 

 friction of ice on water particles, whereby, as was first shown by 

 Faraday^^ and afterwards ascertained by Sohncke,"*^ ice becomes 

 positively and water negatively electrified. Thus tlie layer of air 

 lying above the isothermal of 0° and carrying ice spicules, becomes 

 pesitively electrified by friction Avith the layer lying below the 

 isothermal and containing water particles, and the negative electricity 

 of the latter partly passes down to the earth through precipitation. 



The pliotoelectric theory, which was first proposed by Arrhenius,^^ 

 and then souiewhat modified and fully developed by Elster and 

 Geitei,*^^ considers that the negative electricity of the earth's surfiice is 

 dissipated in the atmosphere by the action of the ultraviolet light 

 from the sun. Some rekitions are traced between the seasonal and 

 diurnal variations and the intensity of the solar radiation. 



The so-called ion-theory of atmospheric electricity was first 

 suggested bv J. J. Thomson, ^^ durinu' his investigaition on the charge 



1) Edlund, Actes de l'Acadeuiie des Sciences de Suéde, XVI. 1878. 



2) Solmcke, Der Ursprim^' der Gewitter-elektricitiit und der gewohnlichen Elf ktiicitii-t 

 der Atmosphäre, Jena. 1885. 



3) Faraday, Experimental Kesearches, II. p. lOt!. 



4) Sohncke, Wied. Ann. 28. P- 550. 1886. 



5) Arrhenius, Meteorologische Zeitschrift, 5. P- -97. 1S88. 



6) Klster und Geitel, Sitzuuf^.sberichte d. Wiener .Akad. \\}[. p. 703, 1892. 



7) J. J. Thomson, Phil. Mag. XL VI. p. 533. 1898. 



