PHENOMENA CONNECTED WITH CLOUDY CONDENSATION.* 



By .T<MIN AiTKEN, F. Iv. S. 



In the tirst part of this commiinicatiou I intend giving; the resnlts of 

 an investigation into the phenomena connected with the chindy con- 

 densation prodnced when a jet of steam mixes with ordinary air, with 

 special reference to the marked change which takes place in the appear- 

 ance of the jet by electrification and other canses. In the second part 

 will be given the residts of an investigation into certain color i)he- 

 nomena, which can be i>rodnced when the condensation is made to take 

 Itlace nnder certain conditions, and it is thought that these exi)eri- 

 mental color i)henomena, if they do not give the ex])lanation of a 

 "green sun," at least enable us to reproduce it artificially with the 

 materials existing in our atmosphere. 



PART T. — STEAM JETS. 



Milieu a jet of steam escapes into the air condensation at once ensues 

 by the expansion and the mixing of the steam with the cold air. The 

 result is the jet becomes distinctly visible by the light reflected by the 

 minute drops of water carried along in the mixed gases and vapor. 

 At first sight there is little that is interesting in the changes then tak- 

 ing place. The subject has therefore attracted but little attention 

 and has been but little studied. This is evident from the great interest 

 that has been taken in the change produced in the appearance of the 

 jet when it is electrified, yet I hoj^e to be able to show that this is only 

 one of a number of causes which alter the appearance of the con- 

 densing steam. 



R. Helmlioltz was the first to show that when an ordinary jet of 

 steam is electrified there is a marked increase in the density of the con- 

 densation. The effect of the electricity is certainly very remarkable. 

 Tlie instant the jet is electrified it at once changes and becomes much 

 denser, and the condensed particles also become visible much closer 

 up to the nozzle from which the steam is escaping. For the conveu- 



*From tlie Proceedimjs of Ihe Boyal Society, April 28, 1892; vol. Li, i)p. 403-439. 



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