394 
KEY. S. HAIJGHTON ON THE JOINT-SYSTEMS OF IRELAND 
correlated Secondary Systems of Conjugate Joints, as I believe that they can be shown 
to be simple mechanical consequences of the Primary System (A, C). 
Neglecting for the present the system (A"', C'"), the whole of the Joints of Water- 
ford may be represented by the following diagram (fig. 1), to which 1 shall frequently 
have occasion to refer. 
Fig. 1. 
It will be observed that the Primary System (A) divides somewhat unequally the 
angle between (A') and (A"). 
Angle between A and A' . 
. 25 
45) 
„ C and C' . 
. 28 
26) 
Angle between A and A" . 
co 
co 
16 1 
„ C and C ' . 
. 36 
7) 
Mean = 27 5. 
Mean = 37 11. 
Part I.— ON THE JOINT-SYSTEMS OF THE CO. DONEGAL. 
The following Tables give the bearings of all the joints observed, arranged according 
to their azimuths, together with the locality, and a statement of the rock in which the 
joint was observed. In each locality several joints of the same bearing were measured, 
but only one is recorded. 
Table I. — East and West Joints in Donegal. 
1 No. 
Bearing. 
Dip. 
Locality. 
Rock. 
1 
45 N. of E. 
Between Dunglow and Doocharry. 
Granite. 
2 
45 
Culdaff. 
Quartzite. 
3 
35 
The Mintiaghs. 
„ 
4 
35 
Urrismenagh. 
Granite. 
5 
30 
90 
Gweebarra, South. 
„ 
6 
30 
The Mintiaghs. 
Syenite. 
7 
30 
Gap of Mamore. 
Quartzite. 
8 
20 
Barnesmore. 
Granite. 
9 
20 
Barnesbeg. 
„ 
! 10 
15 
80 N. 
Doocharry Bridge. 
” 
