35 



This experiment was attended with considerable difficulty, 

 as the moisture from the steam seemed to get on to the glass 

 shade over the gold leaves and so form a charged conductor 

 between the leaves and cloud. The cloud was first formed 

 by a jet of steam from a pipe, then by the vapour from a vessel 

 of boiling water, and lastly by a smoke ring or rather a steam 

 ring. By this latter method an insulated cloud was formed> 

 which, as it passed was attracted by the charged leaf. 



Of the two latter propositions I have not been able to 

 obtain any experimental proof I made an attempt, but 

 failed, through the bursting of the vessel in which the cloud 

 was to be formed. I hope, however, shortly to be able to 

 renew the attempt, and in the meantime I will take it for 

 granted that these propositions are true. Faraday main- 

 tained that evaporation was not attended by electrical 

 separation unless the vapour was driven against some solid 

 when the friction of the particles of water gave rise to elec- 

 tricity. So that unless there were some free electricity in 

 the steam or vapour before it was condensed none could be 

 produced by the condensation, and hence the cloud when 

 formed would be uncharged. 



In the same way with regard to evaporation, unless, as is 

 very improbable, the steam into which the water is turned 

 retains the electricity which was previously in the condensed 

 vapour ; the electricity from that part of the cloud which 

 evaporates must be left to increase the tension of the re- 

 mainder. So that, as a charged cloud is diminished by 

 evaporation the tension of the charge will increase, although 

 the charge remains the same. 



I will now point out what I think to be the bearing which 

 these propositions have on the explanation of thunder storms. 

 In doing this, I am met with a great difficulty, namely 

 ignorance of what actually goes on in a thunder storm. We 

 seem to have no knowledge of any laws relating to these 

 every-day phenomena ; in fact we are where Franklin left 



