406 
REV. S. HAITGHTON ON THE JOINT-SYSTEMS OF IRELAND 
Other systems of Joint-Planes occur in the granite of Cornwall, 
observed at Gunnis Lake the following joint-planes: — 
21° E. of N. (Mag.V 
16° 
99° 
55 55 55 
95 55 55 
19 0 40' E. of N. 
and at Trincomlee Hill, 13° E. of N. 
Mr. Whitley has 
And I observed at Carn Brea well-marked joints, which seem to be conjugate to the 
foregoing, viz. 20° S. of E. 
These joint-planes may possibly indicate the System (A" — C") observed in the co. 
Waterford. 
At Carn Marth 1 found joints bearing 40° W. of N., as in the Mourne Mountains. 
The relation between the directions of the lodes and joints in Cornwall has been long 
known. I was desirous of testing it in the Carn Brea district, and therefore asked per- 
mission of the officers of Carn Brea, Dolcoath, and North Roskear Mines to make use 
of their maps for the purpose ; the permission was readily granted, and I have here 
tabulated the results of my investigation. 
Direction of Main Lodes (Mag.), 1840. 
System A. 
No. 
Bearing. 
Name of lode. 
Mine. 
I 
15 N. of E. 
Highbarrow. 
Carn Brea. 
2 
9 „ 
Druid’s. 
3 
5 J> J, 
Teague’s. 
» 
4 
16 „ 
Western part. 
Dolcoath. 
5 
5 „ 
Eastern part. 
6 
11 „ 
South lode. 
„ 
7 
16 „ „ 
Entral, western. 
„ 
8 
5 „ 
Entral, eastern. 
99 
9 
10 „ „ 
Main lode. 
North Roskear. 
10 
E.W. 
» » 
11 
5 N. of E. 
99 99 
99 
Mean 
8 ° 45 ' N. of E. 
Direction of Cross Courses conjugate to Main Lodes. 
System C. 
No. 
Bearing. 
Name of lode. 
1 
° N.S. 
Carn Brea. 
2 
14 W. of N. 
99 99 
3 
6 i> „ 
Great Cross Course, dividing Dolcoath from Cooks Kitchen. 
Mean 
6 ’ 40 ' W. of N. 
