1893.] On Interference Phenomena in Electric Waves. 99 



With this apparatus a series of observations were made for various 

 thicknesses of distilled water. To cover, as far as possible, irregular- 

 ities in sparking, readings were now taken in pairs alternately at the 

 point to be determined and some other point taken for the time as the 

 ^standard ; it would have caused too great delay, and consequent 

 irregularity in the effectiveness of the sparks, were all the water to 

 be siphoned out between each pair of readings. As before, ten or 

 twelve readings were usually taken at each point. The throw ob- 

 tained with no liquid was also always taken as unity. 



As a specimen of the usual spark variations, the following series of 

 readings for the determination of the throw with 55 cm. water with 

 reference to 40 cm. will serve. The series is taken quite at random 

 from the others. 



The readings are grouped separately, but it will be understood that 

 they were taken in pairs alternately. 



The complete results are given in the curve (Fig. 2). It is seen 

 that for such a poor conductor as distilled water the interference 



H 2 



