Colours of Cloudy Condensation. 511 



air charged with phosphorus nuclei passing per second longi- 

 tudinally through a slender tubular condenser K (fig. 3), 



- Fig. 3.— Tubular Electrical Condenser. Scale 1/10. 



/ K I 



lb 



T 



bears a constant ratio to the electrical current passing for a 

 constant potential-difference radially between its surfaces, and 

 that therefore both currents correspond to a definite colour in 

 the' colour- tube, the latter becomes, to some extent, a gal- 

 vanometer. In other words the colour obtained is, under 

 proper graduation, a measure of the current in the condenser. 

 We have thus a new method of estimating to what extent 

 the nuclei take part in the conduction of electric current, for 

 the question is yet an open one whether condensation may 

 not be promoted by a distinct set of nuclei from those which 

 convey electric current. Both, however, must occur pro- 

 portionally to each other; the former, for instance, being 

 later stages of growth of the latter, or produced in other 

 ways from the other. The present experiment admits of an 

 easy modification which will throw some light on the inquiry. 

 In fig. 2, let the tube t be replaced by the slender tubular 

 condenser K (fig. 3), 50 centims. long effectively, internal 

 radius '159 centim., external radius *300 centim., so that the 

 air-space is about *141 centim. thick. Through this cylin- 

 drical shell air saturated with phosphorus emanation is passed 

 at various speeds from the gasometer, entering at a, and 

 leaving, to enter the jet, at b. The external shell of the con- 

 denser is permanently put to earth, the internal shell charged 

 to as high potential-differences as the apparatus warrants, 

 and alternately discharged. The observations were made by 

 looking down the tube C through the window n after adjust- 

 ment for a given colour had been made at F, to ascertain the 

 effect of successively charging and discharging the condenser. 

 For potential-differences of 60, 150, and 300 volts between 

 the shells and for all available colours, not a trace of colour- 

 fluctuation in the steam-tube icas to be observed, due to charging 

 and discharging the condenser ; whereas the slightest turn of 

 the stopcock F immediately changes the colour perceptibly. 

 One concludes therefore that the number of nuclei removed by 

 current is insignificant as compared with the total number 

 present, if, indeed, different nuclei may not respond to the 



