250 
MR. A. W. RUCKER AND DR. T E. THORPE ON A MAGNETIC 
and 
and 
1-85 — H = c (1 - O'OOl c) /24'47 
I — 49‘Sd — c — m (X — 5) 
hi = 0 ‘ l 57 — O’OO l 9 c — 0‘0155 sin (50 c) 
Jbi' values of H > ] '7, and by 
1-7 — H = 0-036854 c 
and 
Z — 53-514 = c - 0-151 (X — 5) 
for values of H < 1 '7. 
The difference between the observed and calculated results in District VIII. (South 
Ireland), is larger than in the other cases. It must, however, be remembered that it is 
absolutely very small. Thus, if the disturbed stations at Galway (which have been 
excluded from the calculations) were introduced, the difference would be reduced from 
•0022 to "0007. As the effect of one station is so great, it is remarkable that the 
discrepancies are not larger. 
District. 
Hovizoutal Foi'ce at central stations. 
Difference 
in terms of 
0-0001. 
Mean of values 
observed in district. 
Calculated. 
]. 
1-5580 
1-5582 
o 
- LJ 
11. 
1-636.3 
1-6358 
+ 5 
HI. 
1-7164 
1-7180 
-16 
IV. 
1-7970 
1-7969 
+ 1 
V. 
1-6650 
1-66.58 
- 8 
VI. 
1-6979 
1-6972 
+ 7 
VII. 
1-8212 
1-8218 
- 6 
VIII. 
1-7053 
1-7031 
+ 22 
IX. 
1-7694 
1-7698 
_ 4 
We conclude this section with a Table, which gives the observed and calculated 
elements at every station. 
In the calculations, graphic methods have been partly used, and, in some cases, this 
may have led to slight differences (which are, however, so small as to be quite unim¬ 
portant) between the values given and those which would be deduced directly from 
the formula!. 
