; in the fourth the number of electrons carried by the drop for each value of
; and in the fifth the number, characteristic of this drop, which is proportional to the charge of one electron. This number is obtained precisely as in the two preceding tables by finding the greatest common divisor of the successive values of (
) and then multiplying this by an arbitrary constant which has nothing to do with the present experiment and hence need not concern us here (see [chap. V]).
It will be seen that though the times of fall and of rise, even when the same number of electrons is carried by the drop, change a trifle because of a very slight evaporation and also because of the fall in the potential of the battery, yet the mean value of the positive electron, namely, 6.697, agrees with the mean value of the negative electron, namely, 6.700, to within less than 1 part in 2,000.
[TABLE VIII]
| Sign of Drop | Sec. | Sec. | ||
|---|---|---|---|---|
| 63.050 | } | |||
| 63.186 | 41.728} | 8 | ||
| 63.332 | 41.590} | |||
| - | 63.328 | |||
| 62.728 | 25.740} | |||
| 62.926 | 25.798 | 11 | ||
| 62.900 | 25.510 | |||
| 63.214 | 25.806} | } | ||
| Mean = 62.976 | } | |||
| 63.538 | 22.694} | 12} | ||
| 63.244 | 22.830} | |||
| 63.114 | 25.870} | |||
| 63.242 | 25.876 | 11 | ||
| + | 63.362 | 25.484} | ||
| 63.136 | 10.830} | |||
| 63.226 | 10.682 | |||
| 63.764 | 10.756 | 22 | ||
| 63.280 | 10.778 | |||
| 63.530 | 10.672 | |||
| 63.268 | 10.646} | } | ||
| Mean = 63.325 | } | |||
| 63.642 | } | |||
| 63.020 | 71.664} | 6 | ||
| 62.820 | 71.248} | |||
| 63.514 | 52.668} | |||
| + | 63.312 | 52.800 | 7 | |
| 63.776 | 52.496 | |||
| 63.300 | 52.860} | |||
| 63.156 | 71.708 | 6 | ||
| 63.126 | ||||
| Mean = 63.407 | } | |||
| 63.228 | 42.006} | } | ||
| 63.294 | 41.920 | 8 | ||
| 63.184 | 42.108} | |||
| 63.260 | 53.210} | |||
| 63.478 | 52.922 | 7 | ||
| - | 63.074 | 53.034 | ||
| 63.306 | 53.438} | |||
| 63.414 | 12.888} | |||
| 63.450 | 12.812 | 19 | ||
| 63.446 | 12.748 | |||
| 63.556 | 12.824} | |||
| Mean = 63.335 | } |
| Duration of experiment 1 hr. 40 min. | Mean = 6.697 |
| Initial volts = 1723.5 | Mean = 6.700 |
| Final volts = 1702.1 | |
| Pressure = 53.48 cm. |
Since this is about the limit of the experimental error (the probable error by least squares is 1 part in 1,500), we may with certainty conclude that there are no differences of more than this amount between the values of the positive and negative electrons. This is the best evidence I am aware of for the exact neutrality of the ordinary molecules of gases. Such neutrality, if it is actually exact, would seem to preclude the possibility of explaining gravitation as a result of electrostatic forces of any kind. The electromagnetic effect of moving charges might, however, still be called upon for this purpose.