144 



SECTION IX. 

 INCLINATION RESULTS. 



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



January 23 and February 8, 1902. 



The " Discovery " was swung for deviation of compasses 



January 22, in latitude 77 24' S., longitude 169 5' E. ; and 

 February 8, 77 51' S., 165 30' E. 



The resulting deviations are in close agreement and indicate that the magnetic condition of the vessel 

 was the same on both occasions, and it may therefore be assumed that this condition did not alter between 

 the above dates. 



Adopting the notation of the ' Admiralty Manual of Deviations of the Compass,' the mean value of the 

 coefficients of deviation for the compass in the observatory cabin are : 



A. B. C. D. E. 



-025' -13 55' -3 49' + 1 24' +002' 



On January 23, in latitude 77 25' S., longitude 169 30' E., observations for Inclination were made on 

 board, with the ship's head in four nearly equidistant directions, approximating to north, east, south 

 and west. The results of these observations are the only data, obtained in the Antarctic, available for 

 reducing the observations made in these regions. 



Observations for X = Mean Horizontal Force on board ^ constant ratio whkh hag guch an important 



Absolute Horizontal iorce 

 bearing on all observations made on board, were obtained at 



Spithead, August, 1901 giving result 0-975 



Lyttleton, June, 1904 0-976 



Falkland Islands, July, 1904 0-970 



Spithead, September, 1904 0-973 



Mean 0-973 



From the results of observations for Inclination made by Mr. BERNACCHI and Lieutenant ARMITAGE 

 during their sledge journeys, and from those made by Mr. BERNACCHI at the Ice Station, McMurdo Sound, 

 a preliminary chart of lines of equal Inclination was drawn, from which the absolute Inclination at the 

 position of swinging, January 23, was estimated to be 86 25' S. 



The values observed on board were, 



o o / 



with ship's head, (1) N. 4 E. (magnetic), 87 41 Inclination S. 



(2) S. 81i E. ( ), 86 21 



(3) S. 3 W. ( ), 85 37 



(4) S. 82 W. ( ), 87 12 



The formulae adopted for determining the errors of Inclination due to the direction of the ship's head are 



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

 for all observations made with ship's head between 



NE and NW, 



SE SW, 

 and 



s cos + N = {(1-2 sin D) sin f - sin C} cosec f tan ff 



