1879.] Observations of the Arctic Expedition, 187 5—76. 31 



remarkable, as it proved, for an absence of brilliant auroras, and in 

 which no connexion was observed between the appearances of that 

 phenomenon and movements of the declinometer magnet. 



Hourly observations were made with the differential declination 

 magnetometers, and on all occasions of great disturbance special 

 observations at frequent intervals. At Floeberg Beach continuous 

 hourly scale readings were taken during portions of December, 1875, 

 and January and February, 1876 — in all 37 days ; and at Discovery 

 Bay from the 23rd October, 1875, to the 28th March, 1876, with only 

 a break of two days in November, and a few hours in February. 



The greatest range of the declination was observed on the 19th 

 February, 1876, about the same hours, at Floeberg Beach and Dis- 

 covery Bay, reaching 5° 9' '4 and 5° 47' "9 respectively. The smallest 

 range was observed on the 12th January, when only 0° 4' was recorded 

 at the first-named station, and 0° 6'*9 at the last. On an average, 

 about every eighth day the higher values of the daily range were 

 attained, and comparing the highest with the lowest scale reading 

 during the whole period, it shows that the magnet moved over 8° of 

 arc. 



The mean daily ranges for the several months or the square root of 

 the mean of the squares of the daily ranges for each month expressed 

 in arc, are : — 



Floeberg Beach. Discovery Bay. 



1875. December = 71 "4 1875. October - 93'3 



1876. January = 68"5 „ November = 90'2 



„ February =110"9 „ December = 69'6 



1876. January.., = 723 



„ February = 93*7 



„ March = 108*2 



At Discovery Bay, therefore, the mean daily range gradually de- 

 clined in value from October to December, when the minimum range 

 was reached, but again increased during the subsequent months of 

 observation. 



Comparing the results of the mean daily range during the whole 

 period with those obtained at Floeberg Beach and Yan Rensselaer 

 Harbour * — stations where the inclination and horizontal force differ 

 so little from the same elements at Discovery Bay — it is found that 

 the mean daily range at Van Rensselaer Harbour was 2° 28' "6 ; Floe- 

 berg Beach, 1° 3F-5; Discovery Bay, 1° 28'*0. 



The hours of the greatest easterly and westerly deflection of the 

 declinometer magnet in its mean daily departure from the normal, 

 differed considerably from those of the middle northern latitudes, 

 where 8 a.m. and 1 to 2 p.m. are the well-established hours. 



* Yan Rensselaer Harbour lies S. 17° W. 196 miles from Discovery Bay. See 

 " Smithsonian Contributions to Knowledge," vol. x, 1858. 



