CAPTAIN ELLIOT’S MAGNETIC SURVEY OF THE INDIAN ARCHIPELAGO. 325 
same day, than there will be after the lapse of some time at the same hours ; thus, 
there would be a much greater difference in the time of vibration of a needle at 
11 A.M. and 5 p.m. on the same day, than if it were vibrated at 11 a.m. on different 
days. 
The following Table contains the probable error of a single determination, and 
also of the mean value of the horizontal intensity, at each station in the Eastern 
Archipelago. 
No. of 
Number of 
Number of 
Mean value of 
Probable error 
Tear and Month. 
Name of Station. 
observa- 
tions. 
deflecting 
needles. 
instru- 
ments. 
the horizontal 
intensity. 
Of a single 
determination. 
Of the mean 
value. 
1845 
Singapore 
179 
2 
2 
8-095 
+ -009 
+ -0007 
March, 1846 
Singapore 
55 
7 
2 
8-121 
-0095 
•0013 
March, 1848 
Singapore 
199 
5 
2 
8-116 
-0090 
•0006 
December 
Singapore 
300 
5 
3 
8-114 
-0103 
•0006 
January, 1846 ... 
Pulo Peesang 
18 
7 
1 
8-092 
-0070 
•0017 
January 
Carimons 
15 
6 
1 
8-077 
-0090 
•0056 
February 
Lin gin 
16 
6 
1 
8-062 
-0070 
•0017 
June 
Sarawak 
43 
7 
1 
8-186 
-007 
•001 
September 
Batavia 
56 
7 
1 
7-894 
-010 
•0014 
July, 1847 
Batavia 
218 
6 
1 
7-891 
-0084 
•0006 
August 
Lampongs, Sumatra . 
24 
6 
1 
7-916 
-0070 
•0014 
September 
Bencoolen 
24 
6 
1 
7-913 
-0053 
•0011 
October 
Padang 
24 
6 
1 
7-962 
-oil 
•002 
March, 1848 
Ophir, near Malacca . 
20 
5 
1 
8-255 
-017 
•0038 
May 
Pulo Labooan 
20 
5 
1 
8-240 
-0052 
•0012 
May 
Sambooanga 
60 
5 
2 
8-162 
-0110 
•0015 
June 
Keemah 
60 
5 
2 
8-253 
•0120 
•0015 
August 
Cocos 
120 
5 
2 
7-274 
•010 
•0009 
February, 1849 ... 
Nicobar 
60 
5 
2 
8-155 
•Oil 
•0014 
January 
Pulo Binding 
20 
5 
1 
8-117 
•006 
•0014 
January 
Pulo Penang 
Hastings’ Island 
20 
5 
1 
8-159 
•007 
•0015 
March 
20 
5 
1 
8-177 
•007 
•0015 
April 
Moulmein 
59 
5 
2 
8-119 
•0085 
•0011 
August 
Madras 
127 
5 
2 
8-078 
•0085 
•0007 
Table H. 
Table H, at pages cliv and civ, contains the absolute determinations of Total Force, 
and of the Horizontal Component, of Inclination and of Variation. 
Explanation of Table H. — The first five columns require no explanation. The sixth 
column contains the horizontal intensity deduced from observations made with the 
four declinometers ; the values of the horizontal intensity given by the portable de- 
clinometer, are less than those found by means of the other three declinometers ; this 
has arisen from the shrinking of the oak deflecting bar of the portable declinometer, 
by which the values of r, r', &c., the distances of the deflecting from the suspended 
magnet, are less than they should be, consequently the angles of deflection are greater 
than they ought to be ; ^ is therefore greater and X less than its true value ; but this 
shrinking must have happened before the Survey ; for the ratio of the true horizontal 
