322 CAPTAIN ELLIOT’S MAGNETIC SURVEY OF THE INDIAN ARCHIPELAGO. 
November 22, 1845. — Value of one scale division =l'-002 
H (= torsion force) 
^ ( = magnetic directive force) ’ ‘ 1 00 4 
March 21, 1846. — Value of one scale division . . . =59"'983 = l' nearly, 
1 + p =1-0004 
March 7? 1848. — Value of one scale division =1'-0081 
1+f =1-0007 
On returning to the observatory, in December 1848, after an absence of several 
months, I found that the pillar supporting the instrument was slightly inclined, the 
foundation having been undermined, probably by white ants ; I rebuilt the pillar, 
and the instrument being readjusted, the value of one scale division= l'-0005. 
The value of one scale division of the Induction Inclinometer has been already 
stated = l'-0. 
The value of one division of No. III. Declinometer was determined at Samboo- 
anga, May 31, 1848. 
By measuring the scale, with the aid of the horizontal circle, the value of one scale 
division has been ascertained =l'-0036 
JJ 
and 1 + P . . . =1-00037 
The value of one division of C 15, the suspended collimator magnet of the Portable 
Declinometer, was determined from time to time ; but the following are the results 
with two theodolites. 
By the large altitude and azimuth, value of one scale division . =2'-904 
By the small theodolite =2-900 
Mean value 2-902 
Tlie value of one scale division of C 7 the deflecting collimator magnet, was found 
to be =2'-342. 
(2.) Coefficient of Temperature . — The coefficient of temperature, or value of q, 
was determined by vibrating the needles in an oak box, and increasing the tem- 
perature of the room in which the magnets were vibrated. Perhaps the coefficient 
of temperature has not been sufficiently well determined ; but as the standard tem- 
perature to which the magnets are reduced is 80°, and the temperature of the de- 
flecting magnets never differed materially from this, a slight error in the determi- 
nation of the coefficient would make no perceptible difference in the resulting value 
of X. 
Experiments were carried on at Woolwich, at the end of last year, with one of the 
needles ; the coefficient of temperature was determined for the cylindrical magnet 
