398 
REV. S. HAUGHTON ON THE JOINT-SYSTEMS OE IRELAND 
limited number of observed planes, which was 15^ in Donegal, and only 7 in Waterford, 
where this conjugate system is very subordinate in -p-g g 
importance. 
The annexed diagram (fig. 3) shows the Donegal 
joints divided into two conjugate systems, (A, C) and 
(A'", C'"), together with one plane (A') of a third 
system ; all of which are represented in the co. 
Waterford. 
Of the whole 64 joints recorded, 44, or 69 per cent., 
are involved in these five planes ; and the number of 
observations belonging to each is placed beside its 
designation in the diagram. 
If we combine together the systems (A, A'") and 
(C, C'"), we obtain the following as the most simple 
combination of joints observable in Donegal. 
No. of observations. Magnetic bearing. 
I. Primary System (A— A'") . . 15 . . 0° 24' S. of E. 
II. Conjugate Primary (C— 0") . 24 . . 2° 55' W. of N. 
III. Secondary System (A') ... 5 . . 32° 0' N. of E. 
True bearing. 
26° 16' N. of E. 
29° 35' W. of N. 
58° 48' N. of E. 
The angle between the Primary System and its Conjugate (A, C) is therefore found 
to be 93° 19'. 
And the angle between the Primary and Secondary Systems (A, A') is 32° 24'. 
The angle between (A, C) and (A', C') in the co. Waterford has been already stated 
to be 27° 5'. 
Part II.— ON THE JOINT-SYSTEMS OE THE MOURNE AND NEWRY MOUNTAINS. 
The following Tables contain the observed joint-planes of the Moume and Newry 
mountain district. 
Table V. — North and South Joints of the Mourne and Newry Mountains. 
No. 
Bearing. 
Dip. 
Locality. 
Eock. 
1 
45 W. of N. 
° 
Railway cutting *. 
Granite. 
2 
45 
70 N. 
3 
45 
90 
Back of Eagle Mountain. 
„ 
4 
45 
65 N. 
Campbell’s Quarry, Newry. 
5 
45 
90 
» ,, 
6 
30 „ 
90 
Summit of Eagle Mountain. 
7 
30 4 „ 
55 E. 
Killowen. 
Slate. 
8 
30 
60 E. 
” 
” 
* The railway cuttings are from the Main Line Station of the Dublin and Belfast Junction Railway to the 
open plain under Slieve Gullion. 
