290 CAPTAIN ELLIOT’S MAGNETIC SURVEY OF THE INDIAN ARCHIPELAGO. 
The instruments in use at the observatories were the following : — 
No. I. Portable Declination Magnetometer, showing changes of declination or 
of variation. 
No. II. Induction Inclinometer, showing likewise changes of declination. 
No. III. Jones’ new Declinometer, in use during the latter period of the Survey, 
showing likewise changes of declination. 
Nos. IV. and V. Portable Bifilar Magnetometer with Thermometer, showing 
changes of horizontal intensity. 
Nos. VI. and VII. Barometer and Thermometer; Newman’s Standard Barometer was 
in use during the first part of the Survey; and latterly, a Portable Instrument by Cary. 
Nos. VIII. and IX. Dry and Wet-bulb Thermometers. 
No. X. Standard Thermometer. 
Nos. XI. and XII. Maximum and Minimum Thermometers. 
Observatories, Position of the Instruments, ^c. 
As all the observatories were constructed upon the same principle, it will not be 
necessary to give the positions and adjustments of the instruments at more than two 
of the stations ; the details of the rest being precisely of a similar nature ; for this 
purpose the position of the instruments, their adjustments and the dimensions of the 
observatories on Direction Island, Cocos ; and at Batavia, are given. 
Observatory on Direction Island, Cocos or Keeling Islands. 
The observations at the Cocos or Keeling Islands were made on Direction Island, 
with the usual magnetic and meteorological instruments. The soil on Direction 
Island consists of a few inches of vegetable soil, and of several feet in depth of frag- 
ments of coral. The observatory tent was pitched in the midst of a thick plantation 
of cocoa-nut trees about 8 feet above the level of low- water mark, and about 50 yards 
from the sea. 
Dimensions of the tent 19X13 feet. Tent consisted of a 
double lining of canvas, and the walls of cocoa-nut leaves. 
a. Declinometer No. I. 
b. Declinometer No. II. 
c. Declinometer No. III. 
d. Bifilar and Thermometer. 
e. Barometer and Thermometer. 
f. Dry and Wet Bulb. 
<r. Standard Thermometer. 
The magnetic instruments were placed at the four 
corners as remote from one another as the dimensions 
of the tent would permit. The Standard Thermometer 
was attached to one of the poles of the tent. The Baro- 
meter fixed to a detached post firmly imbedded in the 
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