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 f + C cos f+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 



y 



-^ + d tan = A (' Antarctic Manual '), 



the following procedure was adopted : 

 If Z be the absolute vertical force, 



(a) 1 +d+ -^ = p. (' Admiralty Manual of Deviations '). 

 Z 



At Spithead . . . Z = +0-438 and p. = 0-985, 

 Falkland. . . Z = -0-280 /* = 0'961. 



Using these values in the above formula (a), 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 6. 



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 f tan 6' 

 and 



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



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



y 



A = + d tan 6 

 AjH 



and applied to the values of N. 



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



TABLE XV. Inclination Results. 

 From Observations on board the " Discovery " at Sea, by Mr. BERNACCHI and Lieutenant ARMITAGE. 



