SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY I, I88G. 73 
and in like manner 
(HI _ 
H ~ ~ Y’ 
dm dT 
m T 
Thus, if we use the mean of the times for deducing two values of H and m from 
the two deflection experiments (as is done in the ordinary method of reduction) we 
may obtain the independent values of H and m by altering the means in the ratio of 
the independent to the mean times. 
Thus, at Horsham, the mean time of vibration was 4®'1650, and using this the 
deflections at the two distances gave 
and 
H = 1'8365 and 1’836G 
m = 0-0091956 and 0-0091952 
respectively. 
The actual jDeriods of vibration for 100 oscillations observed were— 
Apparently— 
Moving to right. 
Moving to left. 
m. s. 
m. s. 
6 56’6 
6 56'G 
56'5 
56-6 
56'5 
.5G-5 
56-5 
56-G 
56-3 
5G'4 
56-4 
5G-5 
Taking the means of the observations recorded above and below the line we get for 
the time of one oscillation 
4^-1655 and 4^-1645. 
These independent times differ from the mean by 0-012 and — 0-012 per cent, 
respectively. 
Hence, altering the values of H and m in the same proportion, but in the opposite 
direction to that indicated by the signs of these cjuantities, we get 
and 
MDCCCXC.-A. 
H = 1-8363 
and 
1-8368, 
m — 0-0091945 
and 
0-0091963. 
L 
