MAGNETIC OBSERVATIONS. 



81 



of motion at Port Foulkc (42') when compared with that of Van Rensselaer (69'); 

 this may be due to the short scries of observations at either place, and partly also 

 to disturbances. The horizontal force at Port Foulke being smaller than at Van 

 Rensselaer, and the former station having been occupied during a maximum of the 

 ten or eleven year inequality, the latter during a minimum of that cycle, we should 

 have expected the greater range at Port Foulke. 



The two diurnal curves are further illustrated by means of the accompanying 

 diagram. 



Diurnal Variation in Winter. 



Midnight 



_ i 1 



1 i 1 1 1 



1 1 1 1 1 1 1 



1 







/ .-^"" _ 



2 







/ "-. 



3 







■\ 



4 



_ 







5 

 6 



I 





/ y — 



% 

 8 



" 



,.'-?*'/^ 



_ 



9 

 10 

 11 



Noon 



- P 



i 



«* .' .^^ 





v9 



— 



1 





/ 



_ 



2 



^ 



-^. \ 







3 





~^\^ 



_ 



4 





\^-^. 







■^r"^- 





5 



" 







6 



~ 



~~ ~~~-'; 



^ 



7 

 8 

 9 



: 







10 



- 





>-~-^, 



11 



Midnight 



"' 1 



! 1 1 1 1 



1 111 1 1^1 ~ 





35' 30 



25 20 15 10 5 



5 10 15 20 25 30 35' 



+ (West) — (East) 



Comparing the diurnal progression of the several stations, we find them to 

 exhibit the max-imum west deflection about 1 P. M., which, I believe, holds good 

 for all places in the north magnetic hemisphere. It has also lately been observed, 

 quite close to the magnetic pole, by Sir Francis L. McClintock^ at Port Kennedy, 

 in latitude 72° 01', and in longitude 94° 19' west, magnetic declination 135° 47' 

 west (1858-59). At the Whalefish Islands (Boat Island ^ = 68° 59', \ =- 53° 13') 

 near Godhaven, Lieut. Foster^ found, in June, 1824, the maximum west deflection 

 about \\ P.M. The morning maximum east deflection appears to be subject to 

 certain fluctuations, but it keeps within the limits of midnight and 9 A. M. ; its 

 epochal variation is mostly due to the interferences of the disturbances which, for 



' Phil. Trans. Roy. Soc, 1863, Part II. Results of hourly observations of the magnetic declina- 

 tion made by Sir Francis L. McClintock and the officers of the yacht " Fox," at Port Kennedy, in 

 the Arctic Sea in the winter of 1858-.59, etc. By Maj.-Gen. E. Sabine. 



" Phil. Trans. Roy. Soc. 1826, Part IV. Observations on the diurnal variation of the magnetic 

 needle at the Whalefish Islands, by Lieut. H. Foster, June, 1824. 



11 June, 1865. 



