AND COBNWALL, AND THEIE MECHANICAL OEIGIN. 
397 
From Table III. it also appears that between 30° and 35° North of East, there are 
five observations, whose mean is 
V. 32° O' N. of E. from 5 observations = 8 per cent. 
The accompanying diagram (fig. 2) is a graphical repre- 2 - 
sentation of Table III., and shows sufficiently well the 
five systems of joints that have been deduced from that 
Table. 
Of the joints themselves, I. and III., II. and IV. are 
evidently conjugates, being nearly at right angles respect- 
ively, while V. belongs to a system different from the others. 
Adopting the notation used by me already * in my paper 
on the Joints of the co. Waterford, and comparing the results 
there obtained with those here found, we may construct the 
following Table : — 
Table IV. — Comparison of the Joints of Donegal and Waterford. 
(C). 
West of North (Magnetic). 
(A). 
North of East (Magnetic). 
(C). 
West of North (true bear- 
ings f). 
(A). 
North of East (true bear- 
ings). 
Donegal. 
Waterford. 
Donegal. 
Waterford. 
Donegal. 
Waterford. 
Donegal. 
Waterford. 
7° 33' 
6° 57' 
6° 7' 
7° 46' 
34° 13' 
31° 37' 
32° 47' 
32° 26' 
Angle of Axes = { g* 0 f*/ Waterford } from East to North> 
(C"'). 
East of North (Magnetic). 
(A"'). 
South of East (Magnetic). 
(C"'). 
West of North (true bear- 
ings). 
(A"'). 
North of East (true bear- 
ings). 
Donegal. 
Waterford. 
Donegal. 1 
Waterford. 
Donegal. 
Waterford. 
Donegal. 
Waterford. 
5° 32' 
9° 30' 
7° 51' 
10° 0' 
21° 8' 
15° 10' 
CTi 
OO 
14° 40' 
Angle of Axes = • 
{ 9<C 30' Waterford } from East *° North - 
(A'). 
North of East (Magnetic). 
(A'). 
East of North (true bearings). 
Donegal. 
Waterford. 
Donegal. 
Waterford. 
32° 0' 
33° 31' 
31° 20' 
31 49' 
The agreement between the respective systems A, C and A' is very remarkable ; that 
between A'" and C"', in the two localities, is perhaps as good as can be expected from the 
* Philosophical Transactions, 1858, p. 333. 
t The magnetic variation in Donegal was 26° 40' W. and in Waterford- 24° 40' W. 
