PHENOMENA CONNECTED WITH CLOUDY CONDENSATION. 203 



at once becomes dense and remaius in that condition while the discharge 

 continues. The electrified body may however electrify the jet by 

 induction. If for instance the electrified body be a sphere, and the 

 nozzle from which the steam is issuing be pointed, the electricity dis- 

 charged by the nozzle will electrify the particles, and the condensation 

 becomes dense. But if the nozzle be not pointed, then the presence of 

 the electrified body produces no change, as there is no discharge of 

 electricity. But if now we hold a needle, or other pointed conductor 

 near the jet issuing from the rounded nozzle, ifc at once becomes dense 

 by the induction discharge from the point. In place of a point in the 

 last experiment, we may use a flame; in fact, we may use any influence 

 which will enable the electrified body to electrify the particles in the 

 jet. 



Another way of making this experiment is to insulate the boiler, and 

 electrify it. If the nozzle be pointed, the jet becomes dense on electri- 

 fication; but if it be rounded, the electrification has no eftect. If, how- 

 ever, we bring a needle or a flame near the rounded nozzle, the jet 

 becomes dense. To get no ettect from the electrification it is necessary 

 that the nozzle be a ball of some size, the orifice through which the 

 steam issues being, of course, the same diameter as that of the pointed 

 jet. 



The eftect of the electrification has been studied by R. Helmholtz and 

 by Mr. Shelford Bidwell,* but neither of them seems to be satisfied 

 with any explanation offered. Mr. Bidwell, from a spectroscopic exam- 

 ination of the light transmitted through the jet under the two condi- 

 tions, came to the conclusion that in the dense condition the particles 

 were larger than in the ordinary form of condensation ; and he thinks 

 that the increase in size is due to the electricity causing the small drops 

 of water to coalesce and form larger drojjs. In support of this explana- 

 tion, he quotes Lord Rayleigh's experiments on the coalescence of drops 

 in water jets "while under the influence of electricity. As Mr. Bidwell 

 does not put forth this opinion as final, there is less reason for hesita- 

 tion in stating that the conclusion I have come to is diametrically 

 opposed to Mr. Bidwell's. 



There seems to be no doubt that electricity will act on these very 

 small drops of water in the same way as it acts on the drops in a jet of 

 water. That its action is similar is easily proved by the following 

 experiment with mist drops : Take a small open vessel full of hot water — 

 it is better to color the water nearly black for convenience of observa- 

 tion — a cup of tea without cream does very well for the puri)ose. Place 

 the cup on a table between the window and the observer. On now 

 looking at the cup from such a position that no bright light is reflected 

 from the surface of the liquid, there will be seen what looks like scum 

 on the surface of the tea. That scum is, however, only a multitude of 

 small mist-drops, which have condensed out of the rising steam and 



* L. E. D. Phil. Mag., February, 1890, vol. xxix, pp. 158-162, 



