512 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
idle wires embraced the eleventh stratum from the positive, and deflections were 
obtained as under with ^ shunt:— 
With r shunt. 
Without shunt. 
To left 180- 
= 
1785- 
To right 170 + 
— 
1686 + 
70 + 
= 
694 + 
To left 204- 
= 
2023—* 
To right 110 + 
----- 
1091 + 
„ 140 + 
= 
1386 + 
„ 130 + 
= 
1289 + 
,i 30 + 
= 
297 + 
1-5 + 
= 
149 + 
To left 20- 
198- 
With tube No. 362 hydrogen charge and a battery of 2400 cells, the strata were 
tongue-shaped as in Part II.,t Plate 15, fig. 11; two touch points 1 inch (2 - 54 centims.) 
apart were connected with a Thomson galvanometer. It was noticed that there was 
a strong deflection to the left (the deflection through a wire being to the right) when 
the base of a stratum touched the idle wire nearest the positive terminal and its apex 
pointed in the direction of the negative, but rose above it towards the opposite dia¬ 
meter of the tube, fig. 29, 3. When the apex of the tongue pointed in the reverse 
position so as to touch the idle wire next the negative and the base went to the other 
side of the tube above the idle wire near the positive, fig. 29, 4, then the deflection 
was in a contrary direction (that is the same as through a wire). When the tongues 
crossed the axis of the tube nearly at right angles, then there was an oscillation of 
the needle, first in one direction then in the other, according as the strata altered 
their position slightly with regard to the direction of the apex and base of the tongue. 
The following are the readings without any shunt:— 
140 left - 
20 right + 
15 left - 
210 right + 
200 „ + 
165 „ -r 
150 „ -r 
210 left - 
Sometimes when a deflection took place in the same direction as the current through 
a wire, and had arrived at its maximum, then a slow oscillation was observed in the 
deflection, the needle moving backwards and forwards for about 20 divisions when the 
full deflexion was 290, or 0'068 of the total deflection. 
* Nearly equal to 1 volt through a megohm, 
t Phil. Trans, for 1878, Vol. 169. 
