CAPTAIN ELLIOT’S MAGNETIC SURVEY OF THE INDIAN ARCHIPELAGO. 313 
Latitude. 
The observations for latitude were usually taken, if the weather permitted, a few 
minutes both before and after noon: the instrument being* previously in adjustment, 
the altitudes and times corresponding were taken immediately before or at noon, 
three times with the vertical circle direct, and three times at or immediately after 
noon with the vertical circle reversed ; the latitude was found from these altitudes 
reduced to the meridian. 
A Table of the Latitudes at the Cocos or Keeling Islands is subjoined, merely as a 
specimen of the working of the instrument ; it is necessary to state, that in the ob- 
servations for latitude by taking altitudes of the sun, the error of collimation was cor- 
rected by the reversal of the telescope on its axis ; but in finding the latitude from 
altitudes of the stars, the instrument was clamped in the meridian, the altitude of 
the star taken as it passed the centre wire, and a correction applied for the error of 
collimation. 
Date. 
Latitude 
O 
Date. 
Latitude 
# . 
Name of * . 
August 26 
12 05 21 S. 
August 28 
12 05 18 S. 
a Herculis. 
27 
06 15 
05 32 
a Ophiuchi. 
31 
06 10 
September 10 
05 07 
y Aquilae. 
September 7 
05 30 
05 30 
a Aquilae. 
15 
05 46 
05 40 
£ Aquarii. 
23 
05 19 
05 20 
p, Aquarii. 
26 
06 07 
12 
06 20 
p Piscium. 
27 
05 58 
05 40 
s Piscium. 
13 
05 10 
s Piscium. 
14 
05 30 
[X, Ceti. 
05 30 
0 Piscium. 
15 
05 45 
i 2 Ceti. 
05 20 
fx. Ceti. 
16 
05 10 
A Tauri. 
17 
05 28 
y Aquilae. 
05 30 
a Aquilae. 
Longitudes. 
The longitudes were found chiefly from sights ; but I am afraid they are not much 
to be depended upon, in consequence of the rate of the chronometer frequently 
changing ; the following is the method I adopted, at any two places far apart, where 
I was able to determine the rate. 1 took the mean rate and applied it to the observa- 
tions for longitude at the intermediate stations. At some of the principal points, where 
I remained for a considerable time, I was able to obtain sights of moon-culminating 
stars for longitude, as well as lunar distances ; the longitudes obtained from moon- 
culminating stars with the altitude and azimuth instrument, were necessarily very 
rough, but they served as a check upon the chronometer. 
2 s 
MDCCCLI. 
