38 



RESULTS AND DISCUSSION OP THE 



The index error to needle No. 2 we find by direct comparison with needle No. 1 

 on the followmff dates : — 



May 



17, 



1S42 



October 



11, 



1842 



July 



18, 



1843 



August 



24, 



1843 



Mean +1.'7 



+0.7 

 +1.1 



to Lloyd No. 3, +10.'O 



" +10.3 



" " + 9.8 



" +10.00 



September 12, 1843 



The correction to the Lloyd needles No. 1 and No. 3, A end north, we obtain also 

 by direct comparison, viz : — 



August 29, 1843, correction to Lloyd No. 1, +4.'0 

 September 5, 1843, " " 



September 12, 1853, " " 



Mean correction, +1.9 



The corrections for polarity to needles 1 and 2 in 1843, are determined as follows: — • 



For needle No. 1. Mean dip in 1843 from 34 results, A north, 710 62.'4 



B north, 71 53.8 



Mean dip 71 58.1 



Hence correction to needle 1, A north, — 4.'3, and B north + 4. '3 



For needle No. 2 we have the following differences : — 



May 17, 1842, A north — B north . . . — 8.'4 -| 



October 11, 1842, •< ■• ... —11.9 | 



July 18, 1843, " " . . . + 3.3 



August 24, 1843, " " 



September 12, 1843, " " 



Hence correction to needle 2, A north +1.'8, 



The above corrections have been applied. 



Mean — 3.'6 



+ 1.4 I 

 — 2.2 J 

 B north, — l.'S 



Recapitulation of Monthly Means of the Inclination. 



Month. 



18-12 



1843 



71°+ 



1844 

 71°+ 



January . 

 February . 

 March 

 April 

 May . 

 June . 

 July . 

 August 

 September 

 October 

 November. 

 December . 















57. '5 

 58.4 

 59.5 

 59.0 

 61.3 

 60.7 

 57.2 

 60.2 

 61.2 

 60.6 

 64.1 

 61.7 



54.'9 

 63.2 

 57.7 

 57.5 

 60.5 

 60.7 

 54.8 

 56.4 

 57.7 



56.'2 

 59.5 

 58.6 

 55.9 

 57.1 

 57.3 

 58.9 



Mean ..... 



60.1 



58.2 



57.6 



The preceding results indicate an annual diminution of the dip of 1.'2. To com- 

 plete the dip for the year 1843, the values for January, February, and March have 

 been interpolated by taking the means of 1842 and 1843 of these months respectively. 

 The interpolated dips are 71^ 56. '9, 58. '9, and 59. '0. We have the final values: — 



Dip for 1842.5 72° Ol.'l 



" 1843.5 71 58.2 



" 1844.4 .71 57.6 



