﻿149 



the values of the coefficients B and C were obtained, and the deviation of the compass calculated by means 

 of the formula (' Admiralty Manual of Deviations ') 



Deviation = B sin {'+0 cos i+D sin 2^, 



assuming the coefficients A and E to be zero. 



To obtain the values of V, the vertical force on board due to permanent magnetism, and d, the coefficient 

 of the vertical force due to induction in soft iron, of the formula 



V 



AiH 



+ d tan = A [' Antarctic Manual '), 



the following procedure was adopted :- 

 If Z be the absolute vertical force, 



(a) l+d+ -= = fj. ('Admiralty Manual of Deviations'). 



AtSpithead . . . Z = +0-438 and /x = 0-985, 

 „ Falkland . . . Z= -0-280 „ /x = 0-961. 



Using these values in the above formula («), the resulting values of V and d are 



V = +0-0037, 

 d = -0-0218. 



Then for each inclination observation the correction due to the vertical force of the ship (A) was 



calculated by means of the formula 



A = -^ + d tan 9. 

 AiH 



The process of reduction of the observations for Inclination was as follows : — 



The deviation of the compass having been calculated and the observed readings of the Inclination 

 corrected for instrumental differences, the value of N was calculated for each observation by means of the 



formulae 



s cos f+N = (cos f+sin B) sec (' tan 6' 

 and 



s cos f + N = ((1-2 sin D) sin f - sin C} cosec f tan 0' (see Section IX.). 



The correction due to the vertical force of the ship was calculated from the formula 



A = -Xf + d tan d 

 AiH 



and applied to the values of N. 



The resulting values of absolute Inclination are given in the following table : — 



Table XV. — Inclination Results. 

 From Observaiinns on board the " Discovert/ " at Sea, by Mr. Bernacchi and Lieutenant Armitage. 



Date. 



Latitude, S. 



Longitude, E. 



luclmation, S. 



Observer. 



1904 

 February 20 

 23 



27 



21 



23 



24 



27 



March 1 



2 



4 



75 34 

 73 13 



70 4 



164 42 

 170 2 

 172 25 



Off Cape Washington. 



3' E. of Coulnian Island. 



A few miles N. of Possession Islands. 



70 20 

 67 34 

 67 14 

 67 22 



171 10 

 169 23 

 164 10 

 155 21 



87 24 

 86 58 



86 1 



87 45 

 86 54 

 86 20 

 86 4 



84 8 



85 33 



86 24 



I Lieutenant Aemitaob 

 j with L.C. Circle No. 143. 



I Mr. Beekacchi with Fox 

 I Circle No. 29. 



