148 
FIFTH REPORT- 1835. 
which expresses the ratio of the force at the two stations in a 
form suited to logarithmic calculation. 
The following table gives the results of this computation. It 
contains the place and date of observation; the angle # cor¬ 
rected for temperature ; and the total intensity at each station, 
compared in the first instance with Dublin or Limerick, and in 
the second with London. 
For the intensity of the magnetic force at Dublin we have the 
three following determinations: 
Aug., Sept. 1834 . . Xnt. = TO 194 
Sept. 1835 . 1-0213 
Oct., Nov. 1835 . 1-0211 
Mean.= 1-0206 
The intensity at Limerick, compared with London, is observed 
to be 1-0262; and the intensity at the same place, compared 
with Dublin, is L0030. Accordingly, for the determination of 
the values of the total force at Dublin and Limerick, observation 
furnishes us with three results, in the two former of which the 
intensities at these two stations are directly compared with that 
at London, while in the third they are compared together. To 
infer from these data, therefore, the most probable values of the 
force at the two stations, we must proceed precisely as in the 
analogous problem respecting the horizontal intensities, and we 
have only to substitute in the formulae already given*, for «, b , c , 
&c. their particular values. We have then 
a = 1-0206, b = 1*0262, c = 1-0030, 
c, — — = 1 *0055, c. — c — *0025. 
a 
And since the comparison of Dublin and London is the mean of 
three distinct comparisons, while each of the other two results 
is inferred from one only, the weights may be assumed as follow: 
A = 3, B = 1 , C = 1 . 
Substituting these values, therefore, in the formulae alluded to, 
we find 
o x = + "0004, d y = — -0011 ; 
x = « + £# = T0210, y — b + §y = 1*0251. 
The numbers in the fifth column of the table are deduced from 
those in the fourth, by multiplying by one or other of these 
numbers,—according as the force at the station in question has 
been compared in the first instance with that at Dublin or with 
that at Limerick. 
* Page 134. 
