74 
ME. A. W. KtiCKER AND DR. T. B. THORPE ON A MAGNETIC 
These quantities are quite independent, except as regards the temperature correc¬ 
tions and instrumental adjustments, and their difference is a measure of the errors of 
observation and imperfect compensation of the diurnal variation and disturbance. In 
tabulating the Force observations we give the G.M.T. at which the deflection and 
vibration observations were made, and the extreme temperatures during the progress 
of the experiments, the observed deflections and the independent times calculated as 
above described. 
The agreement of the times of vibration serves to test the vibration experiments. 
As a measure of the accuracy of the deflections we take the ratio of the two values of 
'»i/H calculated by combining the mean time of vibration with each of the two 
deflections. 
The logarithms of these two quantities occur in the calculations, and all that is 
necessary is to subtract them and look out the corresponding natural number. As 
this quantity is very nearly unity we multiply by 100 and give the fractional part 
only. The symbol e is thus the percentage difference between the results given by 
the two deflections when combined with the mean time of vibration. 
The following form, which is that wdiich has been used, explains itself 
The results of the deflections differed by 0*008 per cent., the times of vibration by 
0^*001. There was no disturbance, and the Horizontal Force, owing to diurnal variation, 
was 0*0007 and 0*0003 metric unit above the average, at the times which correspond 
to the middle of the deflection and vibration experiments respectively. 
The corrected values are obtained from the mean values by applying the corrections 
for diurnal variation and disturbance. 
Horizontal Force. Horsham. Observer, A. W. iR. Magnetometer 60. 
Deflection. 
Date, 1888. 
G.M.T. 
t. 
Observed deflection. 
e. 
A- 
April 21 
li. m. 
14 44 
O 
11-8 
to 
10'7 
0 ‘ // 
21 61 55 
9 0 8 
+ 0'008 
+ 0-0007 
0 
Vibration. 
Date. 
G.M.T. 
t. 
T. 
-To. 
A,. 
li. m. 
O 
s. 
Am il 21 
13 34 
16-5 
4-1655 
to 
+ 0-0003 
0 
17-4 
4-1645 
