CAPTAIN ELLIOT’S MAGNETIC SURVEY OF THE INDIAN ARCHIPELAGO. 291 
ground. The Dry and Wet-Bulb Thermometers were placed on a small table, 5 feet 
above the ground. 
Observatory at Batavia. 
The dimensions of this building were 42x28 feet, and almost wholly constructed 
of bamboo ; the walls were 12 feet in height, com- 
posed of thick bamboo matting, and the roof was 
thatched with leaves of the Neepa palm. The soil 
was a very stiff clay, and the spot selected was in 
the midst of extensive rice-fields. 
a. Bifilar Magnetometer, on a pillar constructed 
of sun-dried bricks, capped by a slab of granite. 
h. Declinometer No. II. on a wooden stand. 
c. Declinometer No. I. on a pillar of sun-dried 
bricks. 
d. Standard Barometer with its Thermometer. 
e. Dry and Wet Bulb. 
f. Standard Thermometer. 
The Bifilar at the N.E. angle, the scale facing 
the south ; Declinometer No. II. at the point h, 
and Declinometer No. I. at the point c, both facing 
the east, the instruments being about 18 feet 
apart ; the Dry and Wet Bulb on a table at e; the 
Standard Barometer attached to a post firmly im- 
bedded in the earth at d\ the Standard Thermo- 
meter fixed to a post at f. 
Times of Observation. 
Having during the greater part of the Survey but one assistant, I limited the 
observations to nineteen hours daily, viz. hourly observations from 3 a.m. to 9 p.m. 
To this arrangement there are exceptions ; as at Sarawak and during the first four 
months at Batavia, when I had three assistants ; and then observations were taken 
hourly during the twenty-four hours. By astronomical time, therefore, the obser- 
vations generally commenced at fifteen hours, and terminated at nine hours. 
Order in which the Instruments will be noticed. 
The instruments will be noticed in the following order : — The Declinometers, the 
Bifilar, the Dry and Wet-Bulb Thermometers, the Barometer, the Standard Thermo- 
meter, and the Maximum and Minimum Thermometers. 
Declinometers. 
There were never less than two declinometers observed at the same station, and 
subsequently, when Jones’s declinometer was received, all three were put in adjust- 
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