CAPTAIN ELLIOT’S MAGNETIC SURVEY OF THE INDIAN ARCHIPELAGO. 305 
date of observation ; the number of days and the number of hours of each day the 
instruments were observed; the mean of the dry and wet thermometer, and of the 
tension of vapour ; determined in two ways, — 1st, by dividing by the number of hours 
during which the instruments were observed, and 2nd, by the system of equal inter- 
vals, a method for determining the mean value where the continuity of hourly obser- 
vation is broken during the day, as generally occurred in the present instance. 
Dr. Lloyd, in a paper on the mean results of observation, has shown that the error 
committed by taking the mean of any three equidistant hours as the mean tempe- 
rature of the day, does not exceed 0°-26. In the following Table, in the column con- 
taining the mean by equal intervals, three sets of equidistant hours have been taken 
for finding the mean, viz. 3, 4, and 5 a.m. ; 11 a.m., noon, and 1 p.m. ; 7, 8, and 9 p.m. 
At those stations, where the instruments were observed during the twenty-four hours, 
a direct comparison can be instituted for ascertaining the correctness of this mode 
of finding the mean ; at Sarawak for three and at Batavia for four months, the means 
by each method are nearly identical. The mean temperature, as shown by the dry 
bulb, is about 80° ; the mean of the wet bulb is between 76° and 77° ; and the mean 
elastic force or tension of vapour throughout the space included in the Survey, varies 
from 0’8 to 0‘9 of an inch of the barometric column. 
Table showing the Means of the Dry and Wet Thermometers and of the Tension of 
Vapour, by Dr. Lloyd’s method of equal intervals, and by dividing by the number 
of hours observed, and the difference in each case. 
station. 
Latitude. 
Longitude. 
Mean date 
corresponding 
to the 
1 No. of days. 1 
No. of hours. 1 
Dry Thermometer. 
Wet Thermometer. 
Tension of Vapou-. I 
Mean h} 
equal in 
tervals. 
Mean bj 
number 
of hours 
Diff. 
Mean bj 
equal in- 
tervals. 
Mean by 
number 
of hours 
Diff. 
Mean b; 
equal in 
tervals. 
Mean bj 
number 
of hours 
7 1 
Diflf, 9 
Moulmein ... 
16 29 46 N. 
o / // 
97 45 30 E. 
Mid. of April 
7 
19 
86-1 
88-3 
-J-2-2 
78-0 
78-5 
4-0-5 
•853 
■846 
-•007 
Madras 
13 04 09 
80 16 00 
Begin, of Sept. 
34 
19 
84-3 
85-2 
-I-0-9 
76-6 
76-6 
00 
•811 
•801 
-•010 
Nicobar 
9 10 12 
92 48 23 
Begin, of Feb. 
5 
19 
79-3 
80-5 
+ 1-2 
75-8 
76-6 
-f-0-8 
•839 
•855 
+•016 
Sambooanga . 
6 54 20 
122 13 45 
End of May. 
6 
19 
80-5 
82-2 
+ 17 
76-4 
77-6 
+ 1-2 
•847 
•877 
+•030 
Pulo Penang. 
5 25 36 
100 24 38 
End of Jan. 
5 
19 
806 
81-2 
+0 6 
77-0 
77-3 
-I-0-3 
•873 
•876 
+•003 
Pulo Binding 
4 12 48 
100 32 52 
End of Jan. 
3 
19 
82-7 
83-2 
+0-5 
76-6 
77-1 
+0-5 
•838 
•844 
4- -006 
Sarawak 
1 33 54 
no 29 00 
Mid. of June. 
26 
24 
79-8 
79 6 
-0-2 
77-8 
77-7 
-0-1 
•913 
•911 
-•002 
Mid. of July. 
27 
24 
790 
78-9 
-01 
76-9 
76-9 
0-0 
-886 
•885 
-•001 
Mid. of Aug. 
19 
24 
790 
78-8 
-0-2 
767 
76-6 
-0-1 
•877 
•874 
-•003 
Keemah 
1 21 55 
125 07 59 
End of June. 
10 
19 
80-4 
81-1 
+07 
76-6 
770 
+0-4 
•863 
•865 
4- -002 
Pulo Peesang 
1 27 53 
103 19 15 
Mid. of Jan. 
5 
18 
80-6 
80-8 
+0-2 
77-5 
77-9 
+0-4 
•892 
•905 
+•103 
Singapore ... 
1 18 32 
103 56 30 
End of Nov. 
16 
19 
80-3 
803 
00 
77-1 
76-9 
-0-2 
•876 
•869 
-•007 
Begin, of Dec. 
14 
19 
80-2 
80-1 
-01 
76-4 
76-2 
-0-2 
•851 
•843 
-•008 
Padang 
0 58 58 S. 
100 31 15 
End of Oct. 
13 
19 
78-5 
79-7 
+ 1-2 
75-9 
75-7 
-0-2 
•816 
•828 
4- -012 
Mid. of Nov. 
26 
19 
79-2 
80-2 
+ 1-0 
75-4 
760 
+0-6 
•828 
•835 
+•007 
Mid. of Dec. 
26 
19 
79-5 
80-6 
+1-1 
75-3 
75-9 
4-0-6 
•820 
•826 
+•006 
Begin, of Jan. 
13 
19 
79-8 
80-9 
+ M 
761 
76-7 
4-0-6 
•848 
•855 
4- -007 
Bencoolen ... 
3 53 54 S. 
102 28 45 
Begin, of Sept. 
5 
19 
78-1 
79-3 
+ 1-2 
76-3 
77-0 
+ 0-7 
•869 
•865 
-•004 
Batavia 
6 09 52 
106 58 00 
Mid. of Nov. 
19 
24 
80-3 
80-2 
-01 
76-8 
76-8 
0-0 
•866 
•866 
•000 
Mid. of Dec. 
26 
24 
79-7 
797 
0-0 
76-6 
76-5 
-0-1 
•866 
•859 
-•007 
Mid. of Jan. 
25 
24 
79-5 
79-8 
+0-3 
76-3 
76-4 
4-0-1 
•852 
•854 
4- -002 
Mid. of Feb. 
24 
24 
79-5 
79-5 
00 
76-8 
70-8 
0-0 
•875 
•874 
-001 
Mid. of March 
27 
19 
80-5 
81-2 
+07 
77-2 
77-6 
+0-4 
•882 
•888 
4- -006 
Mid. of April 
26 
19 
80-5 
811 
+0-6 
77-0 
77-3 
4-0-3 
•874 
■877 
4- -003 
Mid. of May 
26 
19 
80-2 
80-9 
+07 
76-5 
76-8 
4-0-3 
•858 
•859 
4- -001 
Mid. of June 
26 
19 
80-0 
807 
+07 
75-4 
75-7 
4-0-3 
•815 
•817 
4--002 
Cocos 
12 05 38 
96 50 30 
Mid. of Sept. 
26 
19 
79-6 
79-5 
-01 
75-0 
75'0 
0-0 
•802 
•803 
4- -001 
Some doubts have arisen as to the value of the dry and wet bulb as an instrument 
MDCCCLI. 2 R 
