produced in Gases by Rontgen Rays 8fc. 427 



2^ minutes. We thus see that our method is amply sensitive 

 to the conductance produced in glass by heating. 



The differences of potential concerned in the experiments 

 described in the last paragraphs were not more than two or 

 three volts per centimetre of paraffin or per half-millimetre of 

 glass. 



To extend our experiments to higher voltages we used the 

 two-leyden method described in § 2. In the experiments on 

 paraffin the ley den A was the aluminium cylinder filled with 

 paraffin in which an insulated metal — now connected to the 

 inside coating of B — was embedded, already referred to. 

 With this arrangement we found that with a difference of 

 potential up to 2500 volts per centimetre of paraffin, no 

 increase of conductance was produced by the Rontgen rays. 



In the experiments with glass the leyden A consisted of the 

 glass tube already used. Its inside coating of silver was now 

 connected to the inside coating of B. With glass also we 

 could not find any increase of conductance produced by the 

 Rontgen rays with differences of potential reaching up to 

 2000 volts per half-millimetre of glass. 



§ 4. Analogous Effects produced by Flame and by Rontgen 

 Rays. 



Two similar sticks of paraffin, which we shall call G and D 

 respectively, each of about 4 sq. centim. cross section, were 

 coated throughout half their lengths with tinfoil. These tin- 

 foils ought to be each metallically connected to the case of the 

 electrometer. 



To obtain a sufficiently delicate test for their electric state, 

 a metal disk of 3 centim. diameter was fixed horizontally to 

 the insulated terminal of the electrometer. 



The two pieces of paraffin were first diselectrified by being 

 held separately in the flame of a spirit-lamp. Their non- 

 tinfoiled ends were then pressed together, and their electric 

 state tested after separation. It was found that they were 

 still free from electric charge. After this, D was charged by 

 being held over the pointed electrode of an inductive electric 

 machine. The quantity of electricity given to it in this way 

 was roughly measured by noting the electrometer reading 

 when the paraffin was held at a disiance of 4 centim. above 

 the metal disk connected to the insulated terminal of the 

 electrometer. 



The free ends of C and D were again held together, and, 

 after separation, both pieces were tested separately. The 

 charged one, D, had suffered no appreciable loss, and the 

 other, 0, induced an electrometer reading of a few sc. divs. 

 in the same direction, when held as near as possible to the 



