AND CORNWALL, AND THEIR MECHANICAL ORIGIN. 405 
Pabt III.— ON THE JOINT-SYSTEMS OF CORNWALL. 
The following notice of the Joint-Systems is founded on my own observations, with 
the exception of the two sets of observations made by Sir H. De la Beche and Mr. N. 
Whitley, which I was permitted to copy by tracing from the diagram deposited in the 
Museum of the Geological Society of Cornwall, in Penzance. 
Sir H. De la Beche and other observers have noticed the relation between the direc- 
tions of the lodes and of the joints in Cornwall. This relation is even more intimate 
than they supposed, and extends to the Secondary Joints, which are well represented in 
the mines by the Caunter Lodes, while the Conjugate Joints are represented by the 
Cross Courses. 
Joint-Planes observed in Cornwall. 
System A. 
No. 
Bearing. 
Dip. 
Locality. 
Bock. 
1 
10 N. of E. 
90 
Land’s End. 
Granite. 
2 
E.W. 
90 
Carn Bosavern. 
„ 
3 
E.W. 
90 
Carn Marth. 
” 
From the MS. observations of Sir H. De la Beche and Mr. N. Wihtley, 
in the Geological Society of Penzance. 
4 
24 N. of E. 
Land’s End. 
Granite. 
5 
21 „ 
,, 
„ 
6 
3 „ 
„ 
7 
6 „ 
Gunnis Lake 
8 
8 S. of E.* 
9 
8 N. of E. 
„ 
10 
14 „ 
11 
6 „ 
12 
9 a 
5? 
13 
10 S. of E. 
Trincomlee Hill. 
» 
Mean 
6 ° 23 ' N. of E. 
| 
System C. 
| No. 
Bearing. 
Dip. 
Locality. 
Rock. 
1 
10 W. of N. 
90 
Land’s End. 
Granite. 
2 
N.S. 
90 
Carn Bosavern, St. Just. 
,, 
3 
N.S. 
90 
Carn Brea. 
.. 
4 
N.S. 
90 
Carn Marth. 
5 
N.S. 
90 
Portreath. 
Slate. 
From the MS. observations of Sir H.Dela Beche and Mr. N. Whitley, 
in the Geological Society of Penzance. 
6 
1 0 W. of N. 
Pedn maen du. 
Granite. 
7 
10 
Carn Clog. 
8 
15 
Carn Creis. 
9 
21 
Mill Bay. 
10 
17 
Carn Barra. 
11 
7 
Carn Mellyn. 
„ 
12 
17 
Tol pedn penwith. 
„ 
13 
7 
Porth Chaple. 
14 
13 
Pedn maen an mear. 
” 
I Mean 
| 9 0 4 ' W. of N. 
