﻿135 



SECTION II. 



Absolute Horizontal Force RESur,T.s. 



The iiistniment used throughout was Unifilar No. 25. 



Magnet No. 25D was used for the observations of dates Ai)ril 17, May 12, May 26, and June 30, 1902. 



In all subsequent observations Magnet 25A was used. 



To obtriin the value of the correction for P (see Admiralty ' Manual of SeientiQc Inquiry '), the mean of 

 the values derived from the whole serie.s of observations with each magnet was taken. 



For Magnet 25D the result gave P = ; for Magnet 25A the result was P -= +0'25. 



The logarithms of the correction factors due to this latter value for the distances used in the deflection 

 observations, viz., magnet at 42 ceiitims. and 56 centims., are respectively 



1-99994 and 1-99996, 



and these \alues have Ijccn used in the reduction of the observations. 



Table I.^Horizontal Force Results. (See figs. 1 and 2, p. 137.) 



SECTION III. 



Absolute Inclination Results. 



The standard adopted for observations of Inclination is the value as obtained with Circle No. 27, 

 corrected for instrumental difference as determined at Christchiirch Observatory. Comparative observations 

 were made with the instrument at Kew before the Expedition sailed, and again on its return, and the 

 results show that the instrument had maintained its condition satisfactorily. The conditions in the 

 Antarctic, however, differ considerably from those at Kew, and it is believed that observations made at 

 Christchurch afford more reliable data for instrumental differences than those at Kew. 



Observations at Christchurch Observatory in December, 1901, and in April, 1904, showed the following 

 differences from the Observatory standard : — 



