362 



Special Reports 



derived from the computation are shown. The correction for No. 6 at the maximum 

 and the minimum is derived in each case from observations at a single station, but at 

 both of these stations the observer suspected the results given by this needle and checked 

 them by repetition. They may, therefore, be accepted as free from accidental error. 

 It sometimes happens that a single accidental variation, apparently not a part of a 

 system, will appear and must be eliminated before the systematic variation is fully 

 defined. Such a point is found in the curve for No. 2 at 36. 27. This outstanding value 

 depends upon the observations at a single station and does not necessarily signify that 

 there is an irregularity in this needle corresponding to this elevation in the curve. It 

 should be borne in mind, however, that the distribution of the four points along any 

 ordinate is determined by the observations and does not depend upon the computation. 

 Any modification of the computation that would result in changing the ordinate of one 

 curve at any point must change the ordinates of the other curves at the same point 

 by an exactly equal amount since this relation is fixed by needle-differences. Hence it 

 will be seen that to reduce the ordinate of the curve for No. 2 at 36. 27 would seriously 

 disturb the curves for both No. 1 and No. 5, while the curve for No. 6 which chances to 



Table 45. Analysis for Behavior of Needles 1, 2, 5, and 6 in Dip Circle No. 177, March to July, 1915. 



Date 



Mean I 



1915 



July 20 



July 17 



July 10, 12 



Mar. 24 



July 5 



July 2 



Mar. 30 



April 1, June 27 



April 2 



June 21 



April 15 



April 5, June 16 



April 11, 24 



June 9, 12 



April 28, June 3 



+32.7 

 + 33 6 

 +34.4 

 +35.2 

 +35.5 

 + 36 3 

 +37.0 

 + 37.6 

 + 38.0 

 +38.3 

 + 38.0 

 +39 

 + 39.6 

 +40 3 

 + 40.7 



Needle difference 



12 



-0.1 

 + 0.9 

 -0.8 

 +0.1 

 + 0.5 

 +3.5 

 -1.6 

 -0.6 

 +0.2 

 + 0.8 

 + 1.0 

 -0 7 

 +0.1 

 + 0.2 

 -1.2 



50 



+0.7 

 -0.2 

 + 1.0 

 0.0 

 -0.9 

 -2.9 

 + 0.4 

 -0.8 

 -1.5 

 -0.6 

 -11 

 + 0.6 

 + 0.1 

 -0.8 

 -0.8 



-0.2 

 + 1.8 

 + 2.3 

 + 7.6 

 +3.7 

 -0.8 

 -4.2 

 +0.1 

 +0.3 

 + 1.9 

 -0 

 + 2 

 + 1 

 + 2 

 + 



61 



-0.4 



-2.5 



-2 



-7 



-3.3 



+0.2 



+5.4 



+ 1.3 



+ 1.0 



-2.1 



+ 0.9 



-2.1 



-1.4 



-16 



+ 1.5 



Adjustment for needle errors 



First trial-term 



+ 

 + 1 

 + 

 +2 

 + 1 

 + 1 

 _2 

 -1 

 -0 

 + 1 

 + 

 + 

 + 

 + 0. 



-1 



+ 

 + 



+1 



+2 

 + 

 -3 

 -0 

 -0 

 -0 

 -0 



-1 

 +1 



+0 

 + 

 + 



-0 



H 

 + 

 + 2 

 + 1 

 + 

 -1 

 + 



+1 



+ 

 + 

 + 

 + 



+ 1 

 + 1 



-0 



-1 



_2 

 -7 

 -3 

 + 1 

 +4 

 +0 

 + 



-1 



+1 



2 



-1 

 -1 



+0 



First error-term 



+ 

 + 

 -0 

 i 

 + 

 + 



-1 



-0 



-0 

 + 

 + 

 -0 

 40 

 -0 



-; 



-0 40 

 -1.97 

 -2.70 

 -7.6S 

 -3.27 

 +0.45 

 +4-47 

 + 0.63 

 + 0.63 

 -1 .77 

 + 1.20 

 -2.37 

 -1.30 

 -1.73 

 -0.09 



Date 



Adjustment for needle errors continued 



Mean 1 



Second trial-term 



1915 



July 20 



July 17 



July 10, 12 



Mar. 24 



July 5 



July 2 



Mar. 30 



April 1. June 27 



April 2 



June 21 



April 15 



April 5, Juno 16 

 April 1 1 , 24 

 June 9, 1-' 

 April 2S, June :; 



+ 32 

 +33 

 +34 

 +35 

 + 35 

 + 36 

 +37 

 +37 

 + 38 

 +38 

 + 38 

 + 39 

 + 39 

 + 40 

 + 40 



-0 

 -0 

 + 

 -0 

 -0 

 -0 

 +0 

 +0 

 + 

 -0 

 -0 

 + 

 -0 

 +0 

 



.04 

 .24 

 .09 

 .03 

 .01 

 .06 

 .41 

 .30 

 .16 

 .15 



13 

 .12 



"5 

 .06 

 .00 



-0. 

 + 0. 

 -0. 

 + 0. 

 +0. 

 

 -0 

 + 

 +0 

 +0 

 + 

 -0 



(I 



+ 



+ 







+ 

 +0 

 + 

 -0 

 +0 

 -0 

 -0 

 -0 

 -0 

 -0 

 + 

 +0 

 -0 

 -0 



1)1) 



.08 

 .18 

 .01 

 .19 

 .21 

 .12 

 .33 



11 

 .06 

 .18 

 .0' 

 .04 



21 

 .19 



S,' 



+ 

 

 

 

 



-0 

 

 

 

 

 

 

 

 



+ 



Second error-teim 



Correction on 

 adopted standard 

 Al = 0.'l-(a + a') 



0. 

 -0. 





 -0. 

 + 0. 

 +0 

 +0. 

 + 

 + 

 -0 

 -0 

 +0 

 -0 

 -0 

 -0 



-0 



+ 11 



-0 

 



+11 



+0 

 -0 

 -0 



+ 

 + u 

 +0 

 -0 

 -0 



j I) 



+0 



+0 

 0. 

 +0 

 

 -0 

 + 0. 

 +0 

 -0 

 -0 

 + 

 -0 

 +0 

 +0 

 -0 

 -0 



No. 1 



+ 0.13 



-o.os 



-0.09 

 -0.01 

 + 0.07 

 -0.08 

 + 0.14 

 -0.11 

 -0.14 

 +0.07 

 + 0.10 

 -0.06 

 -0.02 

 -0.07 

 -0 03 



0.0 

 -0.4 

 +0.4 



0.0 



0.0 

 -0.1 

 + 0.9 

 + 0.8 

 +0.6 

 -0.3 

 -0.3 

 + 0.4 



0.0 

 +0.3 

 + 1.7 



No. 2 



-0.1 

 +0.5 

 -0.4 

 + 0.1 

 + 0.5 

 + 3.4 

 -0.6 

 + 0.3 

 +0.8 

 + 0.5 

 + 0.7 

 -0.3 

 +0.1 

 +0.5 

 +0.5 



No. 5 



+0.6 

 + 0.3 

 +0.5 

 +0.1 

 -0.4 

 +0.5 

 -0.3 

 -0.5 

 -0.7 

 -0.1 

 -0.3 

 +0.3 

 +0.2 

 -0.3 

 -0.3 



No. 6 



+ 0.4 

 +2.1 

 +2.9 

 +7.7 

 +3.3 

 -0.3 

 -4.5 

 -0.4 

 -0.4 

 + 1.8 

 -1.2 

 +2.5 

 + 1.4 

 + 1.9 

 +0.2 



