ON THE ELECTRICAL PROPERTIES OF PURE SULPHUR, 
95 
The following table is a summary of the results of these and other observations, 
and shows how necessary it is to calibrate the galvanometer for each particular throw, 
when these are not large :— 
Table VI., giving Summary of Experiments made on October 17, 1892 ; 
October 25, 1892; and December 1 , 1892. 
Galvanometer period, 14’5 sec. on October 17, 21 sec. on October 25, and 26 sec. on 
December 1. 8 Micrometer divisions cover 1 millim. in the scale image. 
Date. 
Voltage 
in terms 
of 
Clark 
cell. 
Cui’rent, 
in amperes. 
Mean throw 
on reversal, 
in 
micrometer 
divisions. 
Sensitiveness 
for one 
division on 
reversal, 
in amperes. 
Values 
of 0 for 
double 
deflexions. 
. pO 
Sensitiveness for 
one division 
steady deflexion, 
in amperes 
(i.e., current re¬ 
quired to produce 
one division 
steady deflexion). 
Oct. 17, 1892 
2 x icr 3 
2-739 X 10-n 
7-9 
3-5 x 10 -12 
4-53 
1-21x10-11 
5 X 10- 5 
6-85 x 10-n 
18-6 
3 68 x IO- 1 3 
10-32 
1-32x10-11 
•n j ? 
1 x HU* 
1-36 xlO-io 
35-3 
3-85 x 10-n 
18-6 
1-46x10-11 
Oct, 25, 1892 
1— ' 
X 
o 
1 
cn 
1-37 xlO-n 
10-5 
1-31 x 10-12 
6-6 
4 x 10-12 
(mean of 14 
observations) 
Dec. 1, 1892 
5 x 10" 5 
, , 
51-8 
1-32x10-12 
3xl0- 5 
• 
• • 
28-7 
This table requires little comment. If the sensitiveness were reckoned in terms of 
the least visible deflexion, it would appear to be five times greater. The deflexions 
are obviously rather greater for smaller currents than for larger. If we consider what 
has been said about the state of the resultant field, even under such a fairly strong 
control as this, it appears that any simple galvanometric law is not to be expected. 
It is not worth while exhibiting any other tables of sensitiveness, for, though all the 
sulphur observations might be used for the purpose, in general the sensitiveness for 
steady deflexion was not required, and was not calculated.* In the tables giving the 
results by the measurements of the sulphur resistance, the sensitiveness per double 
deflexion (throw) is given, corresponding to each set of observations. For the sake of 
rapidity of observation, the sensitiveness was adjusted to suit the work in hand. We 
do not wish to attempt any comparison between this instrument and those employed 
by other experimenters : our object was to attempt to combine a high degree of sen- 
* Note added September 23, 1893 :— 
We have lately had occasion to use the galvanometer at the highest degree of sensitiveness conve¬ 
niently attainable, in order to study the conduction in films which could not be made very thin. For 
this purpose the period was raised to 25 sec. The terrestrial magnetic conditions were only fairly steady. 
