MAGNET1CAL OBSERVATIONS IN IRELAND. 
155 
Place. 
(tv a 2 ) 
(tv a b) 
(tv b 2 ) 
(w a c) 
(tv b c) 
Cam . 
1156 
— 3876 
12966 
— 1.020 
+ 3-420 
Strabane. 
1764 
— 3696 
7744 
— 1-386 
+ 2*904 
Enniskillen. 
2304 
— 2880 
3600 
— 1-488 
+ 1*860 
Armagh . 
392 
— 1680 
7200 
— *588 
+ 2-520 
Belmullet . 
15625 
- 7375 
3481 
-6-250 
+ 2*950 
Markree. 
17787 
— 12243 
8427 
—9 009 
+ 6-201 
Ballina. 
9604 
— 4802 
2401 
-4-410 
+ 2*205 
Carlingford. 
9 
+ 123 
1681 
+ -030 
+ *410 
Achill Ferry ... 
16129 
— 4953 
1521 
—5*334 
+ 1*638 
Leenan . 
14641 
— 2420 
400 
—4*356 
+ *720 
Oughterard. 
11881 
— 654 
36 
—2'398 
+ ‘132 
Rathdrum . 
4 
— 52 
676 
— -002 
+ *026 
Tulla .. 
7744 
+ 2464 
784 
+ -264 
+ *084 
Ennis . 
9216 
+ 2784 
841 
— *192 
— *058 
Limerick. 
86700 
+ 41820 
20172 
+ 5*100 
+ 2*460 
Clonmel .. 
2809 
I + 3233 
3721 
+ -689 
+ ‘793 
: Ballybunan. 
14641 
+ 5566 
2116 
+ -484 
+ *184 
Broadway . 
9 
+ 201 
4489 
+ -063 
+ 1*407 
1 Waterford . 
961 
+ 2139 
4761 
+ *310 
+ *690 
' Ki Harney. 
14641 
+ 9438 
6084 
+ 1-331 
+ *858 | 
Ferrnoy . 
7396 
+ 6880 
6400 
+ 1*684 
+ 1*520 
| Cork . 
6889 
+ 7221 
7569 
+ 1-577 
+ 1*653 
Glengariff . 
15129 
+ 11931 
9409 
i 
+ 1*353 
+ 1*067 
Adding, we find, 
S (tv « 2 ) = 257431, S (wab)= + 49169, S (w Z> 2 ) = 116509, 
S (w a c) = — 23*598, S (w h c) = + 35*644. 
And the equations are 
257431 x + 49169 y = — 23*598 
49169 x + 116509 y = + 35*644, ~ 
from which we have, by elimination, 
x = — *0001633 = A 
y — + *0003748 = B. 
Finally, substituting these values in equations (H), (I), 
tan u — — 2*2952, u = — 66° 28', r — — *000409. 
The positive branches of the axes of coordinates having been 
assumed to be those which stretch to the north and to the west, 
it follows that the lines of equal horizontal intensity lie to the 
east of north, making an angle of 66^° nearly with the meri¬ 
dian of Dublin ; the horizontal intensity decreases as we pro¬ 
ceed northward, the decrease being equal to the distance tra¬ 
versed in a direction perpendicular to these lines (estimated in 
geographical miles or minutes of latitude) multiplied by the co¬ 
efficient *000409. The lines are laid down in the accompany- 
