278 
TJR. A. W. RttCKER ARD DR. T. E. THORPE OR A MAGRETIC 
We carried a chart with us, and marked the position of each station while on the 
spot. On the average, about four bearings were taken at each station, and at no 
station was the number less than two. 
The bearings of the objects selected were afterwards taken from the chart, and, by 
comparing these with the observations, the Declination was determined. The agree¬ 
ment between the individual observations at each station was in general only 
moderately good, but, even in cases where only two observations were taken, we think 
the means are accurate to about half a degree. 
Throwing out thirteen stations which were evidently highly disturbed, we took the 
mean of the Declinations at the other ten as giving the mean Declination for the 
easterly half of the island, which is 22°‘8. 
By subtracting this from the Declinations found at the stations, we obtained the 
disturbance of the Declination at each. The results are given in the following 
Table 
Station. 
Distui'bance. 
Station. 
Disturbance. 
1. 
0°4 W. 
XIII. 
0°4 B. 
11 . 
1-6 E. 
XIV. 
6-0 W. 
III. 
0-9 W. 
XV. (W.) 
1-9 W. 
IV. 
3-3 W. 
XVI. (S.) 
10-4 E. 
V. 
IT W. 
XVII. (E.) 
3-6 E. 
VI. 
16 E. 
XVIII. (R.) 
II-5 W. 
VII. 
1-5 W. 
XIX. 
5-8 E. 
VIII. 
1-3 W. 
XX. (R.) 
9-9 W. 
IX. 
8T W. 
XXI. (W.) 
25-8 E. 
X. 
0-6 B. 
XXII. (S.) 
10-3 B. 
XI. 
5-8 E. 
XXIII. (B.) 
23-8 E. 
XII. 
0-3 E. 
Stations XV. to XVIII. inclusive were taken round the basaltic mass on the summit 
of the hill behind Kaill, and on the sides indicated by the letters which follow the 
numbers. 
Stations XX. to XXIIl. were in like manner taken round the summit of Compass 
Hill. In both these cases the compass was generally within a foot or two of the 
basaltic columns. The observations, therefore, show that these are powerfully mag¬ 
netic. The disturbing force at Station XXL was nearly half that due to the horizontal 
intensity of the earth’s magnetic field. On the other hand, it is evident that their 
influence diminishes very rapidly with the distance. Station VI. was only a few hundred 
yards from the hill behind Kaill, yet the compass was not affected by more than 1°‘6. 
Stations I., II., III., and IV. are grouped round the southern half of Compass Hill, 
at distances between 200 and 500 yards from the summit; but the largest disturbance 
of the Declination is 3°'3 W. 
Stations XXIII. and II. are situated one above the other on the eastern side of 
Compass Hill, fhe horizontal distance between the two being not more than 80 yards; 
