4 
MAJOE-GENEEAIi SABIKE OX THE DECEXXIAL 
The values are decimals of a minute of arc. The sign + corresponds to Easterly and 
— to Westerly disturbance. 
These variations may be represented by the following formulae : — 
1841—1842 . . A,= -d-085-6-299sin(a+294-7)+{)-lT8sin(2a+298-4) 
1843—1844 . . A,= -0-062-0-231sin(«+294-l)+0-126sin(2«H-319-7) 
1845—1846 . . A,= -0-083-0-273sin(«+283-9)+0-107sin(2a+280-2) 
1847—1848 . . A,= -0-097-0-447sin(a+300-4)+0-227sin(2a+278-6) 
A being the variation at x, the hour required, and a (corresponding to x') counted in 
hours from noon and multiplied by 15°. 
The curves computed by these formulae are sho-wn to the eye in seconds of arc in 
Plate 1. fig. 1. It will at once be seen how thoroughly their inflections accord in cha- 
racter, and at the same time how decidedly and systematically they difier in amoimt. 
The inflections are least in the curve derived from the years 1843 — 1844, and gi-eatest 
in that derived from the years 1847 — 1848. The hour of greatest westerly deflection is 
about 11 P.M., and that of greatest easterly deflection about 7 a.m. The difference between 
the extreme deflections at these hours, or the range of the variation in twenty-four hours 
in seconds of arc, is given by the formulge as follows : — 
1841—1842. 
1843—1844. 
1845—1846. 
1847—1848. 
Easterly extreme 
/« 
. . . 12-0 
II 
6-8 
8-8 
// 
23-7 
Westerly extreme . 
. . . 33-5 
24-7 
27-5 
44-2 
Sum . 
. . . 45-5 
31-5 
36-3 
67-9 
Taking the differences 
between the actual results of the 
observations 
at the same 
hours, or the range of the.variation in twenty-four hours, from direct observation, we have 
as follows : — 
1841—1842. 
1843—1844. 
1845—1846. 
1847—1848. 
Easterly extreme 
/J 
. . . 12-0 
5-4 
// 
11-2 
13-2 
Westerly extreme . 
. . . 35-4 
25-8 
27-6 
49-2 
Sum . 
. . . 47-4 
31*2 
38-8 
62-4 
Thus it Avill be seen, that if we estimate the variation in the mean effect of the 
disturbances, in the course of the decennial period, by the difference in their mean diurnal 
range respectively in 1843 — 1844 and 1847 — 1848, we should infer that theii' mean effect 
is at least twice as great in the year of maximum as in the year of minimum. 
It is probable that if either a higher or a lower arbitrary standard than fom scale- 
divisions were taken as constituting a “ large distinbance,” the inequality between the 
years of maximum and minimiim might be rendered somewhat greater or somewhat 
less, but still not materially so ; the result is of too decided a character to doubt the 
evidence it affords of a subsisting substantial difference between the year's of maximum 
and minimum. 
