ON THE ELECTRICAL PROPERTIES OF PURE SULPHUR, 
93 
nothing in the Laboratory is being moved, and when there is no traffic in the road. 
They are always bad on a windy day ; but this may possibly be attributed to small 
changes of barometric pressure occurring from wind pressure. We are placed at 
about 150 yards from a road along which a steam tram runs, and every time a tram 
comes past, the needle moves about violently ; in fact, w^e often obtain the first 
indication of the approach of a tram from the motion of the needle. All these draw¬ 
backs can only be eliminated by increasing the efficiency of the magnetic screen, and 
this is therefore the next step to take. 
Method of Observation .—In order to obtain the maximum reading for a given 
current, we always obtain a double deflexion, and read the first elongation of the 
needle. Whether this elongation be produced by the current through the sulphur or 
by the derived circuit from the Clark cell, there is practically no induction in the 
circuit, except that in the galvanometer itself. If the derived circuit current be 
adjusted to give the same throw of the galvanometer as the leakage current, we 
consider that the currents must be the same. 
As an example of the behaviour of the instrument, we will give one complete 
set of experiments, at a normal sensitiveness, taken on October 17, 1892, a very 
unsteady day. 
Table Y. — Throws of Galvanometer in Micrometer Scale Divisions. 
Date. 
V oltage. 
Resistance. 
Battery 
position. 
Double deflection. 
Amplitudes from 
special experiments. 
1st—2nd. 
elongation. 
2nd-3rd 
elongation. 
F 
1 Oct. 17, 1892 
2 x 10 -5 , Clark 
P044 X 10 ,; olims 
+ to upper 
terminal 
55 
55 
A—B, 8 divisions 
7 
5 
5 ? 
55 
5 1 
B — A, 7 5 ., 
8 
6 
5 : 
55 
5 ■* 
A-B, 8 
8 
6 
55 
55 
55 
B —A, 8 
75 
5-5 
55 
5 * 
55 
— to upper 
A—B, 75 ,, 
Not 
taken 
terminal 
55 
55 
55 
B-A, 8 0 
5 ' 
55 
55 
A-B, 8-5 
55 
55 
55 
B-A, 7 5 
Mean deflection, 7'9 '3 micrometer divisions. 
Period of a double vibration, 14*5 sec. 
Values of p ,—The ratio of the 2nd elongation to the 1st. 
(1) p = 7/5 = D40, 
(2) p— 8/6 = U333, 
