and the Aurora borealis. 427 



were the case, fog in lower latitudes ought only to betray in- 

 significant traces of electricity, since the conductivity of fog 

 is surely as good as that of the air of the polar regions under 

 ordinary circumstances. Now we know that, notwithstanding 

 its high conductivity, fog is very strongly electropositive. 



The real cause of the above-mentioned results of observa- 

 tion is, in my opinion, that the vertical component of the force 

 of induction, or, in other terms, the force tending to direct 

 the aether (electropositive fluid) from the earth to the air, is 

 very insignificant. The electropositive charge of the air must 

 therefore be feeble, and sometimes so slight that the air be- 

 comes negative by communication with the earth, as is shown 

 by M. Wijkander's observations. The earth itself, on the 

 contrary, must always be electronegative in those regions. 

 If no exterior force acted upon the electric fluid, the earth 

 and ' the atmosphere would be in the neutral state : but as a 

 portion of the electropositive fluid which belonged to the earth 

 has been conveyed into the atmosphere in consequence of the 

 action of the induction-force, the earth itself must be electro- 

 negative. The earth being a good conductor of electricity, 

 and at the same time constituting a spheroid, its negative 

 electricity must be distributed in a pretty equal fashion at its 

 surface ; consequently the terrestrial surface must likewise 

 show itself electronegative in the polar regions, although the 

 vertical component of the force of induction is there very 

 feeble. With the exception of some rare occasions when it 

 was difficult or impossible for him to detect traces of electri- 

 city, M. Wijkander also found that the earth was constantly 

 electronegative. It follows also from the proposed theory that 

 the conductivity of the air in the polar regions should, as M. 

 Wijkander describes, appear greater than at lower latitudes 

 for the same temperature and with the same humidity. If a 

 conducting body placed in the atmosphere is charged with 

 electricity, evidently it must be influenced by the vicinity of 

 an electronegative body so large as the earth. If the conduc- 

 tive body is charged with positive electricity, this electricity 

 is attracted downward by the negative earth ; if the charge is 

 negative, the reverse takes place, for the same reasons. Con- 

 sequently, in both cases the loss of the electricity in the air is 

 accelerated by the negative earth being in the vicinity of the 

 charged body. Now the force of induction of the earth acts 

 upon the electricity of the body in the opposite direction. If 

 the body is electropositive, that force tends to direct the elec- 

 tricity of the body from below upwards, and vice versa if the 

 body is electronegative. Therefore the earth's induction-force 

 tends to diminish the influence of the earth's electricity upon 



