Reductions to Standard Instruments 



19 



Table 3. Dip Corrections on Adopted C. I. W. Standard for the Period 191 1-1913 Continued. 



Instrument 



Type' 



Dip 



Corrections for dip needle 



Tabular 

 designation 



Correc- 

 tion for 

 compass 



Remarks 



Dover circle 17 



(a) 



Dover circle 177. 



(a) 



Dover circle 178. 



(a) 



+47 



+ 10 



-32 



-36 



-40 



-44 



-48 



-52 



-56 



-60 



-64 



-68 



-72 



+70 

 +60 

 +50 

 +40 

 +30 

 + 20 

 + 10 

 

 -10 

 -20 



-62 



-65 



-70 



-75 



-80 



-85 



-90 



Dover circle 201* . 



(a) , 



Dover circle 202 . 



(a) 



-5 

 -30 to - 



+ 55 



+ 50 



+45 



+40 



+35 



+30 



+25 



+20 



+ 15 



+ 10 



45 



No. 6 

 -1'.8 

 -1 .3 



-1 .4 

 -1 .8 

 -2.3 

 -2.8 

 -3.3 

 -3.9 

 -4.4 



No. 6 

 -0'.6 

 +0.2 

 -0.1 

 -0.1 

 +0.2 

 +0.4 

 +0.6 

 -0.4 

 -4.4 

 -8.7 



No. 8 

 -4'.4 

 -3.3 

 -2.7 

 -3.5 

 -2.9 

 -2.5 

 +0.2 



No. 6 

 +2'.3 



No. 6 



-I'.O 

 -1.0 

 -0.9 

 -0.7 

 -0.6 

 -0.4 

 -0.3 

 -0.6 

 0.0 



172.1256 



+0'.l 



>177.1256 



+0'.62 

 -1 .2^ 



178.12378 



(See 

 remarks) 



201.1256 



-4'.0 



-2'.5 I 



202.1256 



or 

 ^202.1257 



(See 

 remarks) 



-7'.5 



Because of very erratic behavior of 

 needle 6, dips from -30 to -44 

 and from 55 to 56 were 

 rejected; for dips between 60 

 and 67 a further correction of 

 +4'. 5 to the tabulated value 

 was clearly indicated. During 

 1913 needle 2 for dips from 65 

 to 67.7 required a further 

 correction of +3'.0. 



Instrument cleaned and slightly 

 overhauled in October 1911. 

 The analysis of earth-inductor 

 comparisons and field data, 

 available for the period 1911 to 

 1913, indicated with slight modi- 

 fications for dips below +20, 

 corrections substantially the 

 same as for 1905 to 1910 work, 

 reported on in Volume I. 



Needles supplied with new pivots 

 during latter part of 1910 and 

 instrument generally overhauled. 

 During use by Australasian Ant- 

 arctic Expedition, correction for 

 needle 3 deflected by 4 in total 

 intensity work for dips 62 to 

 90 was +2'.0; the logarithm 

 of total-intensity constant for 

 needle-pair 3 and 4 was 9.55301. 



;FA/=-0'.3+0'.8co3/-0'.4sin/ 



for needle 1 . 

 FA/=-l'.6+l'.9cos/+0'.2sin/ 

 , for needle 2. 



These values apply during 1911 

 and 1912. The pivot of needle 6 

 was broken on May 22, 1911. 

 Needle 7 was used subsequently 

 in place of 6 but was found 

 rather unsatisfactory; results by 

 it for values of dip +23 to +36 

 were rejected, as its behavior in 

 this region of dip was very errat- 

 ic. The corrections adopted 

 for needle 7 for period 1911 and 

 1912 were: +35, -1'.8; +40, 

 -1'.8; +45, -2'.0; +50, 

 -0'.7; +55, +1'.7. 



'For explanation of types, see p. 12. 



^Through September 2, 1911. 



'After September 2, 1911; subsequent to repolishing of pivot and needle blade, and remagnetization of needle, in October 1911. 



'Circle 201 has continued to be very satisfactory. It was possible, with the frequent comparisons for different values of the dip with a 

 standardized earth-inductor at the Carnegie land stations, to improve the correction-formulse for needles 1 and 2; these are, however, practi- 

 cally the same as found for 1905-1910 work. Needles 5 and 6 were used only at 2 stations. 



