14 Bcientifio Proceedings, Royal Dublin Society. 



horizontal adjustable slit, and observed through a low-power microscope. The image 

 of the bubble was clear and distinct, and its size could be determined on the scale- 

 piece of the microscope, which read 25 divisions to 1 mm. 



The first observations taken were on air-bubbles in distilled water. The results 

 of Quincke and McTaggart, that they moved to the positive pole, were verified. 

 McTaggart's results in the case of the alcohols were likewise verified. In ethyl 

 alcoliol bubbles of diameters 0-08, 0-10, 0-12, 0-16, 0-20, 0-24, and 0-28 mm. were 

 observed under a field of 160 volts per em., and showed no motion. In butyl alcohol 

 bubbles of diameters 0'06, 0-12, OIG, and 0-24 mm. showed no motion under a field 

 of 95 volts per cm., being under observation in each case for at least sixty seconds. 

 In methyl alcohol bubbles of 0'20 and 0'32 mm. diameter, respectively, showed no 

 motion under 160 volts per cm. These bubbles were the only two which were success- 

 fully observed, the time of observation being only fifteen seconds. The difficulty arose 

 from the fact that the field had the peculiar effect of causing air-bubbles to dissolve 

 quickly. Tliis phenomenon is mentioned by McTaggart. The following observations 

 may be recorded in this connexion : — With no field in action a bubble of diameter 

 0'08 mm. remained unchanged while observed for forty-five seconds, but dissolved 

 completely within three seconds under a field of 160 volts per cm. Again, bubbles 

 of 0'12, 0'16, and 0-20 mm. diameters disappeared under field within ten seconds. 

 A bubble of 0'20 mm. diameter grew to 0'28 mm. in thirty seconds without a field, 

 and decreased to 0i2mm. in fifteen seconds under field. Another of 0'28mm. 

 diameter gradually dissolved under field in forty seconds. At the same time, none 

 of these bubbles showed any tendency to definite motion under the field. A similar 

 effect of an electric field on the solution of the bubbles was looked for in the other 

 alcohols and other liquids examined, but found to be absent in all cases. Observa- 

 tions were now proceeded with on air bubbles in a number of liquids not previously 

 examined. 



In xylol several bubbles, each of the following diameters, 0'08, O'lO, 0-12, 0-20, 

 0'24, 0'28 mm., were examined, and showed no motion under a field of 160 volts 

 per cm. Each bubble was kept under observation with reverse fields for at least 

 thirty seconds, except bubbles of 0'12 mm. diameter and under. These latter always 

 dissolved quickly, while some of the larger bubbles showed a tendency to grow in the 

 liquid, but in no case did the change in size' affect the neutral attitude of the bubbles 

 to the field. Air-bubbles in benzene were next examined. In the first sample they 

 all moved to the negative pole under field. The benzene was probably impure, as 

 the bottle contained some traces of red rubber cork, portion of which had probably 

 gone into solution. In fresh pure benzene, under a field of 160 volts per cm. for 

 periods of about thirty seconds, various bubbles of diameters 0'06, 0'12, 0'16, 0'20, 

 0'24, 0'28, 0"32, 0'40, and 0'48 mm. showed no motion. There was not the same 

 difficulty with benzene as with xylol in investigating the smaller bubbles, but, as 

 before, some bubbles grew in size while under examination, as, for example, from 

 0'32 to 0-48 mm. diameter, but the change did not afi'ect the neirtral attitude to 

 the field. 



In toluene air-bubbles 0-32 mm. and 0-48 mm. did not move under reversed 

 fields of 95 volts per em. for thirty seconds each way. Another bubble, 0'32 mm. 

 diameter, was under observation for two minutes in the same field, and did not 

 move. A small bubble, 0'12 mm. diameter, gradually dissolved, but was uninfluenced 

 by the field. 



It was now decided to proceed with investigations with benzene derivatives, 

 some of which are chemically neutral, others acidic, others basic, in the hope that 

 the presence of free ions might be the clue to the presence or absence of charge. 



