﻿852 Prof. W. A. Douglas Radge on the Electrification 



in the air and are adsorbed at nil the surfaces of the apparatus, 

 to he afterwards slowly given up spontaneously it' the sur- 

 faces are net freed from them by vigorous heating. The 

 formation of the aggregates in Mr. Owen's experiments is 

 thus due to easily condensed minor constituents of the air, 

 which are first adsorbed and afterwards slowly given up by 

 the walls and the phosphorus pentoxide. as these were not 

 sufficiently heated. 



Also with regard to another paper of Mr. Owen's (Phil. 

 Mag. April 1911, p. 465, "On Condensation Nuclei produced 

 by the Action of Light on Iodine Vapour"), in explanation 

 of effects there described I should like to call attention to 

 our experiments (P. Lennrd and C. Ramsaner, op. cit. 

 Part III.), where we have shown that glass-wool and every 

 glass surface that has not been strongly heated continuously 

 gives off adsorbed minor constituents cf the air. which on the 

 production of ozone by ultra-violet light always lead to the 

 formation of nuclei : now, according to Mr. Owen himself, 

 ozone is forme;! in his experiments. The regeneration of the 

 effect on washing the wall- with distilled water is explained 

 by the fact that the water must contain dissolved small 

 quantities of the vapours and gases mentioned before (for 

 instance. NH 3 ), and as it trickles down give these up to the 

 glass walls through adsorption. These observations led us 

 to construct asbestos filters of combustion glass, which could 

 always be e'eansed by being heated to redness, while glass- 

 wool or cotton-wool filters, which are generally used finally 

 tu free a current of purified air from dust, have just the 

 opposite effect, and charge the air again with all the impu- 

 rities which have been previously removed, thus vitiating 

 the results. All previous work on the action of ultra-violet 

 light on gases, and especially on the formation of nuclei in 

 gases, suffer from this source of error. 

 T am. Gentlemen, 



Your- faithfully, 



Radioloffisches Institut, CARL RaMSAUER. 



Heidelberg, 24 Nov.. 1011. 



LXXXI. A Note on the Electrification of the Atmosphere and 



Surface of the Earth. B>/ W. A. Douglas. Pudge. Pro- 

 fessor of Physics, University College, Bloemfo/dein *. 

 IX the course of some work on the value of the atmospheric 

 potential gradient in South Africa, the author has 

 pointed out the important influence exerted by the clouds of 

 dust raised by the wind. The normal fine weather charge 

 * Communicated bv the Author. 



