592 
MESSRS. R. T. GLAZEBROOK AND S. SKINNER ON THE 
thermometer placed near the cells, rose by about 0°'4 in about an hour previous to the 
experiment, it is probable, therefore, that the E.M.F. of the cells corresponds to a 
temperature some few tenths lower than that given, and that the numbers are slightly 
too high; in any case the differences are small. 
§ 15. Tests on Old Cells in the Cavendish Laboratory. 
The cells of this set have been made at various dates by members of the advanced 
class in practical electricity at the Cavendish Laboratory, and are all of the pattern 
described by Lord Rayleigh (‘Phil. Trans.,’ 1885). Their comparison was begun 
in November, 1889, and has been continued. The standard against which the earlier 
comparisons up to December, 1889, were made is slightly doubtful, and also the 
temperature at which these were made. 
The cells are interesting, for they show the kind of accuracy reached by experi¬ 
menters putting up one or two cells from printed directions, with only such help as is 
usually given by the demonstrator. The materials have been purchased from the 
same sources as they were at the time when Lord Rayleigh was at Cambridge, and so 
they may be taken to be of approximately the same quality. Several cells belonging 
to this set have unfortunately been broken. Cell No. 23, which shows a very high 
E.M.F., is known to have been unsaturated with ZnS0 4 . 
Table III. 
Date. 
Nov. 7, 
1889. 
Nov. 13, 
1889. 
Dec. 3, 
1889. 
Mar. 16, 
1891. 
Mar. 21, 
1891. 
April 21, 
1891. 
May 2, 
1891. 
May 21, 
1891. 
Aug. 11, 
1891. 
Tempera¬ 
ture. 
I 
i " 
13° 
10° 
13° 
16°’4 
15°-2 
17°-6 
Number 
11 
+ 4 
+ 0 
- 4 
+ 1 
- 3 
-3 
-5 
-1 
12 
+ 2 
+ 8 
- 5 
- 0-5 
- 5 
-4 
-6 
-4 
13 
+ 8 
+ 8 
- 1 
- 1 
— 2 
-3 
-5 
-1 
14 
- 4 
+ 2 
- 9-5 
+ 4 
-11 
-4 
-5 
+ 2 
16 
+ 8 
+ 16 
- 0-5 
- 2 
+ 1-5 
+ 7 
-3 
+ 3 
17 
+ 64 
+ 16 
- 5 
-10 
- 5-5 
+ 2 
-3 
+ 6 
19 
. . 
, # 
+ 6 
+ o 
- 6 
- 1 
20 
. . 
, # 
, , 
+ o 
+ 1 
- 2-5 
21 
- 4 
+ 6 
+ 0 
- 2 
- 7 
- 5 
22 
. . 
- 2 
+ o 
+ 2 
- 3 
23 
+ 32 
+ 36 
+ 28 
+ 31 
24 
• * 
+ 8 
+ 2 
+ 2 
+ 0 
+ 1 
In these cells the paste was neutralised with zinc carbonate. 
W e come now to the observations on cells set up for the purposes of this enquiry. 
