mith the Condensation of Vapour. 163 



surface over which the electric force was originally spread is 

 reduced, so that it is by condensation confined to a smaller 

 surface, and consequently ready to exert itself with greater 

 energy, in other words, its tension is increased. If under 

 these circumstances a substance capable of receiving and con- 

 ducting the force is brought into contact with the vapour, the 

 latter parts with its charge, or so much of it as is necessary to 

 maintain an equilibrium between it and such bodies as we 

 have just alluded to. 



We have here presented to our notice two important par- 

 ticulars connected with the ascent of electrified vapour in the 

 process of evaporation — its insulation by the surrounding air, 

 and the increase of electric tension upon its condensation. In 

 connexion with the insulation of the electrified vapour, or as 

 Howard more correctly terms it, "suspended water (not 

 vapour, for that is a gas and therefore a non-conductor)," 

 Howard, in his Climate of London, vol. i. p. 148, has this im- 

 portant passage : — 



" We can scarcely imagine a body more perfectly insu- 

 lated than the^first particle of isoater, which separating from 

 vapour that has ascended into the higher atmosphere, begins 

 to obey the law of gravity. There are two sources from 

 whence such a particle may obtain an electric charge, viz. the 

 surrounding air, and the vapour out of which it was formed; 

 and which may (though in itself non-electric) afford to the 

 water, now reduced many hundredfold in volume^ a real posi- 

 tive CHARGE." 



[The words printed in small capitals were scored by Mr. 

 Howard, those in italics by myself. — W. R. B.] 



It may be remarked in passing, that the views of these 

 authors as to the source of the electric force differ. Read 

 regards the force as rising from the earth. Howard conceives 

 the vapour or aqueous gas to be destitute of electric force, but 

 to exhibit it, or rather to receive a charge on its condensation 

 and resumption oj the form of water. 



We have in the foregoing extract brought clearly before 

 the mind a single drop of water positively electrified and per- 

 fectly insulated. Keeping this insulated electrified drop of 

 water in view, Mr. Howard points out to us the manner in 

 which its electric tension may be, and most probably is, in- 

 creased. In his Introduction, page Ixiv, in speaking of the 

 formation of the cumulus, he says, " On these considerations 

 we are obliged to admit as a cooperating cause of the increase 

 of this cloud, that sort of attraction which large insulated con- 

 ducting masses exercise when charged, on the smaller ones which 

 lie within their influence" viz. " to throw the small otie into an 



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