THE EARTH’S MAGNETIC FIELD IN INTERNATIONAL UNITS. 
453 
Weights of Silver Deposited. 
Temperature of— 
Weight of Silver. 
E.M.F. of cell at 20° C. in inter¬ 
national volts from— 
Cell. 
Resistance. 
1 
Rayleigh 
voltameter. 
Porous pot 
voltameter. 
Rayleigh. 
Porous pot. 
°C. 
°C. 
grams. 
grams. 
18-8 
21-7 
1-6381 
1-6383 
1-0189 
1-0190 
18-6 
21-5 
, 1-6386 
1-6385 
1-0191 
1-0187 
19-8 
23-2 
' 1-6384 
1-6380 
1-0192 
1-0190 
18-8 
21-8 
1-6385 
1-6381 
1-0191 
1-0189 
17-6 
19-8 
! 1-6387 
1-6384 
1-0190 
1-0188 
19-7 
21-9 
1-6387 
1-6379 
1-0193 
1-0188 
19-0 
21-0 
1-6383 
1-6380 
1-0189 
1-0188 
16-1 
17-2 
1-6393 
1-6389 
1-0190 
1-0188 
16-6 
18-3 
1-6388 
1-6386 
1-0189 
1-0187 
17-2 
20-2 
i 1-6389 
1-6383 
1-0191 
1-0188 
17-4 
2M 
i 1-6388 
1-6383 
1-0192 
1-0189 
19-4 
20-2 
1-6389 
1-6381 
1-0192 
1-0187 
20-3 
21-0 
1-6387 
1-6382 
1-0192 
1-0189 
20-0 
20-3 
1-6388 
1-6385 
1-0192 
1-0190 
17-6 
18-0 
2-0015 
2-0009 
1-0190 
1-0187 
Mean 
— 
: — 
— 
1-01909 
1-01884 
The Magnetic Experiments .—An attempt was at first made to carry out the 
magnetic measurements at South Kensington, the earth’s field being also measured 
by means of the magnetometer which supported the coils, which magnetometer had 
been frequently compared with the Kew standard instrument. It was, however, 
found that the magnetic disturbance produced by an electric railway was so great as 
to jirevent observation except at such time as the trains do not run, namely, 
between 1.30 a.M. and 4.15 a.m. Observations were made during four nights, but 
owing to the short time available, during which measurements of H had to be made 
both with the coil and with the magnetometer, and also probably to the fact that 
observing in the middle of the night after a day’s work does not conduce to the 
accuracy with which the magnetometer settings can be made (always a trying 
process), the results were not so concordant as had been expected. 
In this difficulty the Director of the National Physical Laboratory was good 
enough to put one of the magnetic huts at Kew at the author’s disjiosal for a week, 
and so the magnetic observations were made there. This arrangement was a distinct 
advantage, since it obviated the necessity of comparing the value of H at South 
Kensington and at Kew. No silver depositions were made at Kew, but several 
were made immediately before and after the Kew observations. Six of the cadmium 
cells were taken to Kew and were used in turn. These cells were compared with 
the remaining cells which were left at South Kensington before, during, and after 
their use at Kew. The differences however were always less than 1 part in 20,000. 
