XVI 



Introduction to the Makerstoun Observations, 1843. 



The zero used for the observations 1841 and 1842=255*2 {Introduction^ 1841-2, 

 Table 4), was used till Jan. 13. 1843, after which the previous determination was 

 taken, as it was conceived that some change might have occurred at that date in a 

 slight adjustment of the appendages of the magnet, made for the purpose of balanc- 

 ing it. 



2. Observations with the Short Scale. 

 Table 4. — Short Scale Reading at the Magnetic Axis of the Declination Magnet. 



Date. 



Position of 

 Magnet. 



Declino- 

 meter 

 Reading. 



Unifilar 

 Reading. 



Unifilar, minus 

 250 Sc. Div., 



reduced to the 



Declinometer 



r= u. 



Declinometer Reading. 



Mean of 

 two direct 



or 

 inverted. 



Reading 



for 



Magnetic 



Axis. 



Direct 

 minus u. 



Inverted 

 plus u. 



d. li. 



July 31 3 

 Aug. 2 



Aug. 2 3 

 Aug, 3 



Aug. 3 4 



Aug. 3 7 



Direct 

 Inverted 



Direct 



Inverted 



Direct 



Inverted 

 Direct 



Direct 



Inverted 



Direct 



Direct 



Inverted 

 Direct 



Direct 



Inverted 



Direct 



Inverted 



Direct 



Sc. Div. 



148-91 

 147-16 



149-24 

 146-37 

 144-51 



148-90 

 145-75 



146-06 

 150-71 

 14204 



142-66 

 149-50 

 145-78 



157-15 

 136-95 

 157-38 

 137-51 



155-88 



Sc. Div. 



257-15 



258-27 



260-15 

 259-70 

 257-18 



259-41 

 260-10 



259-60 

 255-50 



254-74 



254-28 

 255-46 

 256-74 



267-80 

 268-38 

 267-92 

 266-81 

 266-93 



Sc. Div. 



-f 6-42 

 7-42 



9-11 

 8-70 

 6-45 



8-45 

 9-06 



8-61 

 4-94 

 4-25 



3-84 

 4-90 

 6-05 



15-97 

 16-49 

 16-07 

 15-08 

 15-19 



Sc. Div. 



142-49 



140-13 

 138-06 



136-69 

 137-45 

 137-79 

 138-82 

 139-73 

 141-18 

 141-31 

 140-69 



Sc. Div. 



154-58 

 154-07 

 157-35 



155-65 



154-40 



153-44 

 152-59 



Sc. Div. 

 13910 



137-62 



139-27 



141-24 

 15301 

 141-00 



Sc. Div. 



148-53 



146-58 



147-02 

 146-63 



146-83 



147-34 

 147-16 

 146-80 



The mean reading of the short scale for the magnetic axis = 147'11. 



Corrections to he applied to the Scale Readings at the Magnetic Axis of the Declina- 

 tion Magnets, in oi^der to obtain the zeros of the scales. 



11. Correction for the effects of the bifilar and balance magnets on the read- 

 iness of the declination magnet. 



The effect of the bifilar magnet (by Table 5. of the Introduction to the Obser- 

 vations for 1841 and 1842, north end west) = — 0*64 long scale divisions. 



Sept. 4. 1843, and Jan. 25. 1844. The balance magnet was removed for the 

 purpose of determining its temperature co-efficient. Its effect (north end east) was 

 found = + 0*79 and + 0*80 long scale divisions, on the respective occasions. 



