liquid after having penetrated the glass of the bulb and the sides of the metal tube. The radium may also be allowed to act by placing the bulb beneath the side, d e.
In working with Röntgen rays the course of the rays is through side d e.
The increase of conductivity by the action of the radium rays or the Röntgen rays seems to be produced in the case of all liquid dielectrics; but in order to determine this increase, the conductivity of the liquid itself must be so slight as not to mask the effect of the rays.
M. Curie obtained results of the same order of magnitude with both radium rays and Röntgen rays.
When investigating with the same apparatus the conductivity of air or of another gas under the action of the
Fig. 9.
Becquerel rays, the intensity of the current obtained is found to be proportional to the difference of potential between the electrodes, as long as the latter does not exceed a few volts; but at higher tensions, the intensity of the current increases less and less rapidly, and the saturation current is practically attained for a tension of 100 volts.
Liquids examined with the same apparatus and the same radio-active body behave differently; the intensity of the current is proportional to the tension when the latter varies between 0 and 450 volts, and when the distance between the electrodes does not exceed 6 m.m.
The figures of the following table multiplied by 10—11 give the conductivity in megohms per c.c.:—
| Carbon bisulphide | ............ | 20 |
| Petroleum ether... | ............ | 15 |
| Amylene ...... | ............ | 14 |
| Benzine ...... | ............ | 4 |
| Liquid air ...... | ............ | 1·3 |
| Vaseline oil...... | ............ | 1·6 |
We may, however, assume that liquids and gases behave similarly, but that, in the case of liquids, the current remains proportional to the tension up to a much higher limit
