134 



The " Discovery " was also fitted with the requisite compasses for navigational and observational work 

 on board, and compasses for sledge work. 



Observations made at Kew, before the Expedition sailed and also on its return, showed that the 

 instruments were in good accord with the Observatory standards and had maintained their condition 

 satisfactorily. Observations made at Christ Church Observatory also confirmed this. 



All the available information has been through my hands, and the reduction of the observations has been 

 made by me and checked. The geographical positions were supplied by Lieutenant G. MULOCK, R.N., 

 one of the officers of the Expedition. 



The absolute observations were mainly made in a hut (hereinafter referred to as the Absolute Hut) set 

 up near the vessel's Winter Quarters, its position being in latitude 77 50' 50" S., longitude 166 44' 45" E. 



In November, 1903, a temporary station was erected on the ice in McMurdo Sound, at a distance of 

 1 7 geographical miles from the nearest visible land, and about the same distance from the " Discovery." 



The depth of water under the ice at this station was 200 fathoms, its position being in latitude 

 77 51' 1" S., longitude 166 36' 42" E. 



A comparison of the results of observations made at the Ice Station with those made in the Absolute 

 Hut shows that at the latter position the magnetic conditions were largely affected by local attraction. 



The Horizontal Force was approximately 50 per cent, greater at the hut than at the Ice Station, the 

 Inclination 2 less. The Declination at the hut was about 5 greater (more easterly) than at the Ice 

 Station. 



COMPARISON of Eesults at Absolute Hut with those at the Ice Station. 



Inclination, S. 



Horizontal Force. 



AT THE ICE STATION. 

 Mean of results of observations made November 4, 6, and 8, 1903 . . 



AT THE ABSOLUTE HUT. 



Mean of the values measured from absolute observation diagrams for 

 November 4, 6, and 8, 1903 



86 23-3 



84 34 



0-0433 



0-0686 



DECLINATION. 



At the Ice Station, January 30, 1904. . 

 At the Absolute Hut, January 17, 1904 



147 45 52 K. 

 153 9 50 E. 



All relative observations were referred to values obtained by observation at the Ice Station. 



Absolute observations for Horizontal Force, Inclination, and Declination were made in the Absolute 

 Hut by Mr. BERNACCHI, at intervals averaging a month to six weeks, between the dates April 17, 1902, 

 and January 17, 1904. The results of these observations have in each case been plotted, and curves 

 drawn, from which the approximate change during the year can be inferred, but these results are affected 

 by uncertainties as to the diurnal variation. 



In view of the fact that continuous photographic records of the changes in Horizontal and Vertical 

 Force and in the Declination were obtained by means of the Eschenhagen magnetographs, and are being 

 measured and considered by the staff of the Observatory Department of the National Physical Laboratory, 

 no attempt has been made to derive values of the diurnal variations from the absolute observations 

 themselves. 



The results of the absolute observations afford the means of standardising the values indicated by the 

 photographic curves. 



