402 
MR. E. H. GRIFFITHS OH THE VALUE OF 
Table V. 
The following Table gives a series of observations taken on August 22, 1892 :— 
' 
, Temp. E,„. 
Temp. C. 
Time. 
Battery in circuit. 
I- 
R when 
cR. 
E = -004. 
At which bridge balances. 
5..3.5 
1 Leclanche .... 
344-7 
6.22 
343-9 
20-397 
8-7519 
6.47 
1 Storage .... 
337-8 
20-240 
8-7471 
•0048 
6.55 
6.58 
2 Storages .... 
)? .... 
316-5 \ 
316-7] 
19-698 
8-7311 
•0208 
1 7.15 
1 Leclanche .... 
343-7 
20-395 
8-7518 
7.40 
3 Storages .... 
277-0 
7.45* 
279-0 C?) > 
18-684 
8-7010 
•0507 
7.55 
>) .... 
276-8 
8.17 
1 Leclanche .... 
344-4 
20-409 
8-7021 
9.9 
342-5 
20-361 
8-7508 
9.40 
9.50 
4 Storages .... 
.... 
221 ^ 
2-21-2 
17-286 
8-6600 
•0899 
10.13 
10.22 
5 Storages .... 
1.37 1 
139 J 
15-231 
8-5995 
•1485 
10.44 
1 Leclanche .... 
337-9 
20-243 
8-7472 
When the readings obtained by using 1 Leclanche differ (the change being 
probably due to changes in the temperature of the bridge), intermediate values are 
deduced from the times. 
It seemed absolutely immaterial whether the current was on for only a few seconds 
or indefinitely. In the above set, when three storage cells were being used, the 
current was not broken at all, the calorimeter being cooled down by the ether 
apparatus! in defiance of the heat developed in the coil. Although a quarter of an 
hour elapsed between the observations, they were in very good agreement.^ 
To determine the E.M.F. at the ends of the coil, the various batteries used were 
compared with the Clark cells. This method was therefore open to the sources of 
error mentioned on p. 400, Nos. (2) and (3). The resistance of the other parts of the 
bridge were then determined and were as follows :— 
Resistance of whole bridge 4'30w. 
,, large coils 7'69oj. 
,, coil and its ratio arm 9‘17&>. Hence coil = 8'75, arm '42. 
,, large coils and ratio arm 8‘06co. Hence coil = 8'75, arm '369. 
„ wires forming battery circuit •030<y, 
The E.M.F. ’s were determined by the ordinary Poggendorff’s method in terms 
* This observation was uncertain ; the observer at the galvanometer remarking so, before he kneAV 
that the reading of the temperatui-e was different. 
t See p. 419, infra. 
t Tins would show that the increase in resistance of the other arms of the bridge was not appreciable. 
