170 Mr. W. R. Birt on Atmospheric Electricity. 



energetically into play, and upon the formation of cumulo- 

 stratus and nimbus, the rain is produced in the manner above 

 indicated. 



Throughout the whole of the preceding remarks there is 

 one point presented to our notice with peculiar prominence, 

 viz. the development of the electric force in the act, more or 

 less, of the condensation of vapour. The entire process of 

 nubification appears to be intimately connected with this de- 

 velopment, and the different modifications of clouds entirely 

 dependent on the presence or absence of a disturbed electrical 

 state, not only when the condensation is effected, but when 

 no previous disturbed state exists it may actually be brought 

 about by the condensation of vapour. It may not be toe 

 much to say, that the electricity observed in the atmosphere 

 is principally due to, and the product of condensed vapour. 

 We would of course not regard the condensation of vapour 

 (if the preceding conjectures be correct) as the only source of 

 atmospheric electricity; but we are inclined to regard it as by 

 far the most productive ; and it now only remains to connect 

 the foregoing conjectures and reasoning with such experiments 

 as may be calculated to throw some light on the production 

 of the electric force by condensation. 



Mr. Reuben Phillips has lately detailed in the Philosophical 

 Magazine some very interesting experiments on the electricity 

 of condensation. In one experiment a jet of water was passed 

 through a jet of steam in such a way that the electricity of 

 the water should not affect that of the steam, the water only 

 falling on the wire-gauze of the collector; a negative charge 

 was obtained until the force became sufficiently strong to 

 effect a change in the kind of electricity ; in other words, the 

 jet of water exhibited precisely the same effect as the steam 

 alone. Mr. Phillips attributes this to the drops of water col- 

 lecting negative electricity from the steam : he says, " The 

 negative charge given to the screen was I think only produced 

 by the drops of water collecting negative electricity Jrum the 

 steam^ much in the same way as the wire-gauze did *." 



We here see the drops of water regarded in the light of 

 insulated (?) conductors projected into the midst of condensed 

 vapour. Each particle of this vapour is electrified negatively ; 

 and as the particles of water either come in contact with or 

 sufficiently near to receive the charge of the particles of va- 

 pour, the charge passes to the water-drops, and through the 

 medium of the screen affects the electrometer. It would be 

 very interesting to know, if with a given pressure of steam, 

 such, for instance, as would produce the greatest negative 

 * Page 106 of the present volume of this Journal. 



