43° 



THE POPULAR SCIENCE MONTHLY 



Similarly the charge carried by any captured ion is proportional to the 

 change produced in this sum by the capture. Now the change in this 

 sum produced by the capture of the ion which caused the time in column 

 F to change from 34.8 to 84.5 was, as any one who wishes can verify, 

 .00891 cm. per sec. and the successive values of this sum arranged in 

 order of magnitude were .04456, .05347, .06232, .07106, .08038. If 

 now electricity is atomic in structure all the different charges appearing 

 in this experiment, those on the ions and those on the drop, should be 

 exact multiples of the elementary unit of charge, which means that all 

 of the numbers above given should be exact multiples of something. 

 Dividing the above five numbers by 5, 6, 7, 8 and 9, respectively, gives 

 .008912, .008911, .008903, .008883 and 008931, which are all seen to be 

 within one fifth of one per cent, of the value of the change in the sum 

 of speeds produced by the capture of the ion which caused the numbers 

 in the column F to change from 34.8 to 84.5. Hence the charge carried 

 by this ion was itself the elementary unit out of which all of the other 

 charges which appeared in the experiment were built up. The results 

 on another drop which was observed through a much longer time, 

 namely, about four and a half hours, are given in the following table : 



1 

 2 

 3 



4 

 5 

 6 



7 

 8 

 9 



4.917 Xn 



4.917 

 9.834 

 14.75 

 19.66 

 24.59 

 29.50 

 34.42 

 39.34 

 44.25 



4.917 X » 



49.17 

 54.09 

 59.00 

 63.92 

 68.84 

 73.75 

 78.67 

 83.59 

 88.51 



Observed Charge 



49.41 

 53.91 

 59.12 

 63.68 

 68.65 



78.34 

 83.22 



In this table 4.917 is merely a number obtained, precisely as above, 

 from computing the change in the " sum of speeds " produced by the 

 capture of a particular ion, while the column headed " observed charge " 

 gives the successive values of the sum of speeds. It will be seen that 

 during the experiment this drop carried all possible multiples of the 

 elementary charge between 4 and 18, save only 15. No more exact or 

 more consistent multiple relationship is found in the data which chemists 

 have amassed on the combining powers of the elements, and on which 

 the atomic theory of matter rests, than is found in the above numbers. 



Nearly a thousand different drops have been examined in the manner 

 indicated, some of them being of oil, a non-conductor, some of glycerine, 

 a semi-conductor, some of mercury, a good conductor, and some of other 

 substances, and in every case, without a single exception, the initial 

 charge placed upon the drop by the frictional process, and all of the 

 dozen or more charges which have resulted from the capture by the drop 

 of a larger or smaller number of ions, have been found to be exact mul- 



