220 Prof. Millikan : New Modification of the Cloud Method 



§ 6. The Results. 



The results of all the observations taken by Mr. Begeman 

 and myself, who worked together on all experiments which 

 were made after this method had been worked out, are con- 

 tained in the following tables. The observations marked 

 with a triple star are those which were marked " best " in my 

 notebook and represent those which were taken under what 

 appeared to be perfect conditions. This means that we could 

 watch the drop long enough to be very certain that it was 

 altogether stationary ; that we could time its passages across 

 the cross-hairs with perfect precision, and that it showed no 

 apparent retardation in falling through the two equal spaces. 

 The double-starred observations were marked in my note- 

 book " very good." Those marked with single stars were 

 marked " good" and the others " fair." 



The only observations taken and not recorded in the 

 tables are the following : — 



First, I discarded three very good observations of my own, 

 taken under conditions of potential and position of cross-hairs 

 which made them uncertain in spite of the accurate timing. 

 These observations belong to series No. 2 and would not affect 

 appreciably the final result if they were included. Second, I 

 have discarded three observations which I took on unbalanced 

 drops, timing thnm as they rose against gravity under the 

 influence of the field, and then again as they fell under gravity 

 between the same cross-hairs, when the field was thrown off. 

 Although all of these observations gave values of e within 

 2 per cent, of the final mean, the uncertainties of the obser- 

 vation were such that I would have discarded them had they 

 not agreed with the results of the other observations, and 

 consequently I felt obliged to discard them as it was. In the 

 third place, 1 have discarded one uncertain and unduplicated 

 observation apparently upon a singly charged drop, which 

 gave a value of the charge on the drop some 30 per cent, 

 lower than the final value of e. With these exceptions all 

 of the data recorded in our note-books are given below. 

 Furthermore none of the observations were worked out 

 until after all of the observations had been taken, so that 

 neither Mr. Begeman nor myself had any predispositions as 

 to what should be the correct time of fall in the case of any 

 drop. 



Finally, in order to vary the conditions of the experiment 



