BiFiLAE OR Horizontal Force Magnetometer. 



XXIX 



2d, The same deflecting bar was placed to the north and south of the bifilar 

 magnet, and to the east and west of the declinometer magnet, the prolongation of 

 the axis of the deflector in both cases passing through the centre of the suspended 

 bar. The results are given in the 2d portion of Table 3. 



35. 3c?, A large deflecting bar (15 inches long) was employed in the same manner 

 as the small bar in the 1st instance. 



4cth, The large deflecting bar was employed in the same manner as the small 

 bar in the 2d case. 



36. In the 3d case, deflections of the bifilar could only be obtained to the E, and, 

 in the 4th case, to the S of the bifilar magnet, owing to the proximity of the bifilar 

 to the walls of the Observatory, It was easy, however, from the observations with 

 the small bar to make the requisite corrections for the diff'erence of deflection on 

 the opposite sides : the correction is small. The results for the 3d and 4th cases are 

 contained in the 3d and 4th portions of Table 3. 



Table 3. — Observations of Deflection for the Determination of the Coefficient of 



the Bifilar Magnetometer. 



No. 



of 



Series. 



Deflections of Bifilar Magnet. 



Deflections of Declination Magnet. 



Resulting 

 Value of k. 



Date. 



Distance. 



Deflection. 



Mean. 



Tiierm. 



Date. 



Distance. 



Deflection. 



Mean. 



Therm. 



/ 



1847. 

 May 11 



Feet. 



2-2 1^ 



Sc. Div. 



133-4 

 138-5 



Sc. Div. 



1360 



53-6 



1847. 



May 14 



Feet. 



Sc. Div. 



94-30 

 92-25 



62 43 



62-6 



0-0001345 



1 I 



May 



13 



2-7 1^ 



64-4 

 66-4 



65-4 



61-9 



May 



14 



^■' {'. 



45-85 

 45-00 



30 33 



62-6 



0-0001359 



\ 



May 



12 



3-267|^ 



34-3 

 35-4 



34-9 



58-5 



May 



14 



3.67{« 



24-20 

 23-70 



16 6 



62-6 



0-0001342 



' 



May 



11 



-{^ 



118-4 

 119-6 



119-0 



53-9 



May 



15 



- {^W 



81-60 

 82-40 



55 9 



600 



0-0001350 



2 '■ 



May 



13 



3-167{^ 



60-9 

 60-7 



60-8 



60-9 



May 



15 



3-16'{w 



42-05 



42-75 



28 31 



60-0 



0-0001364 



1 



May 



12 



4-583|^ 



21-0 

 21-0 



21-0 



56-4 



May 



15 



4-583{^ 



14. 34 

 14-58 



9 43 



60-0 



0-0001346 



3 ■ 



May 



May 



15 

 15 



6-9l7{^ 

 8-209{^ 



119-8 

 71-4 



119-8 

 71-4 





May 

 May 



15 

 15 





82-56 

 82-84 

 50-13 

 49-88 



55 37 

 33 38 



61-5 

 61-5 



0*0001351 

 00001370 



4 ■ 



May 



May 



19 

 19 



'•' {w 



7-792{^ 



125-1 

 42-9 



126-0 

 43-0 



55-2 

 55-2 



May 

 May 



15 

 15 



6-833|^ 



102-48 

 103-28 



44-23 



69 11 

 29 45 



61-8 

 61-8 



00001350 

 0-0001357 



37. 5th, In May and August 1847, a theodolite magnetometer by Mr Jones of 

 London was converted into a unifilar horizontal force magnetometer, the suspended 



MAG. AND met. OBS. 1845 AND 1846. h 



