INTRODUCTION. Xili 
TABLE 2.—Value of the Divisions of the Long Scale in the Declinometer during 1842. 
Scale Theodolite Scale Theodolite Value of 100 
Division. Reading. Division. Reading. Scale Divisions, 
o “ ° ‘ “ ° Z “ 
4 51 30-0 240 3 44 22-5 1 7 7:5 
4 44 47:5 250 3 37 40-0 17 7:5 
4 38 5-0 260 3 30 57-5 1 7 7:5 
4 31 20-0 270 3 24 15-0 1 7 50 
4 24 37-5 280 3.17 32:5 1 7 5:0 
4 17 55-0 290 3 10 50-0 1 7 50 
4 11 12:5 300 3.4 7:5 1 7 50 
4 4 30-0 310 2 57 25-0 1 7 5-0 
3 57 47-5 320 2 50 40-0 1 7 7:5 
3 51 5-0 330 244 0-0 1 7 50 
3 44 22-5 340 2 37 17-5 1 7 50 
3 37 40-0 350 2 30 35-0 1 7 50 
3 30 57-5 360 2 23 50-0 1 7 75 
The mean value of 1 Scale division is 06710. 
11. Determination of the point of the scale at the magnetic axis of the bar, or 
the zero of the scale. 
June 28. 1841. Magnet with short scale. 
The torsion having been removed from the suspension thread, and the Reading 
Telescope fixed temporarily, readings were made, the magnet being direct and also 
inverted (the scale and lens below the magnet). 
TABLE 3.—Reading of the Short Scale for the Magnetic Axis of the Declination Magnet. 
Position of 
Mean of each Reading for 
Magnet. 
eae Beating: alternate two. | Magnetic Axis. 
' 
Direct 140-3 
Inverted 159-1 
Direct 139-6 
Inverted 159-5 
Direct 138-5 
Inverted 160-3 
Direct 137-1 
The mean reading for magnetic axis=149°3 Sc. div. 
July 12 till 26.1841. Effect of Bifilar and Balance Magnets (See Table 5), 
+0°3 Sc. div., corrected zero 149:0 Sc. div. 
July 27 till Dec. 28.1841. Effect of Bifilar and Balance Magnets (See Table 5), 
—0°3 Se. div., corrected zero 149.6 Sc. div. 
MAG. AND MET. OBS., VOL. I. d 
