Disjunction-currents ttoough Gases of various Densities, 17 



Experiment 3. — To ascertain whether any change had taken 

 place in the machine, the first experiment was repeated : — 



Deflections. 

 343 

 373 



Mean . . 35-8 



When the coil C was accompanied by the bridge, no indication 

 of induction was observed ; but when, on the contrary, the bridge 

 was removed, the deflection was diminished by more than one- 

 half. 



The following experiments were made in the same manner as 

 the preceding, after the resistance in the rheostat had been 

 doubled. 



Experiment 4.—- The German-silver wire in the circuit :— 



Deflections. 



20-5 



21-5 



21-5 



Mean . . 21-2 



Experiment 5. — C inserted along with the German-silver 

 wire, the latter as bridge to the former : — 



Deflections. 

 21-6 

 20-5 



Mean . . 21'0 



Experiment 6. — The same experiment as No. 4 : — 



Deflections. 

 22-8 

 22\L 



Mean . . 22*4 

 This series, therefore, gave the same result as the first. 



In order to investigate the nature of the electromotive force 

 of disjunction when the spark was formed in various more or less 

 rarefied gases, a glass cylinder 12 centims. in length and 7 cen- 

 tims. in diameter was used. Brass caps could be screwed on 

 air-tight at each end of the cylinder. In the centre of each cap 

 was a stuffing-box, through which a round brass rod could be 

 moved air-tight backwards and forwards. To the inner ends of 

 these brass rods were firmly screwed the poles which were used 

 in the experiments. The outer ends were provided with binding- 

 screws for the conducting-wires ; and on one rod was marked a 

 scale of millimetres, to determine the distance between the poles. 

 The brass rods were insulated from the caps and the stuffing-boxes. 



Phil. Mag, S. 4. Vol. 40. No. 264. July 1870. C 



