OF MAGNETIC DECLINATION AT GOTTINGEN. 



593 



So much regularity appears in the numbers in the last column, 

 that we may hope that the mean value of the secular change 

 4' 15"-4, corresponding to the 1st of Aprils 1837, may not be 

 far from the truth. 



We now proceed to consider the mean values of the declina- 

 tion for each twelve months of our six years' observations, as in 

 the following table : — 



The mean values of the several years correspond to the middle 

 day of the period comprised ; e. g. October 1st, 1834, &c. The 

 means of the six years give the mean declination for the 1st of 

 April, 1837. 



Under the supposition that the mean decrease of the declina- 

 tion is proportional to the time, I have calculated by the method 

 of least squares, frcrm the numbers contained in the last column, 

 the following formula for the declination 8 : — 



8 = 18° 42' 16"'231 -4' 16"-756 . /, 

 where / denotes the interval elapsed since October 1st, 1834, 

 expressed in years. The values of the mean declination com- 



