OF MAGNETIC DECLINATION AT GOTTINGEN. 



595 



no direct determination of the year in which the declination 

 began to decrease in Gottingen. 



We obtain from the formula the yearly change of the decli- 

 nation — 3' 22"-967 — 26"-906 t, corresponding to the interval 

 1834 + / to 1835 + t, where t denotes the time elapsed since 

 the 1st of October, 1834, expressed in parts of a year. 



The influence of the season of the year on the mean values of 

 the declination in the several months, has already been noticed 

 in discussing the differences between the forenoon and afternoon 

 decUnations ; by comparing the monthly means with the decli- 

 nation deduced from the whole year, we may perceive how 

 great this influence is, and the nature of the effects it produces. 

 This comparison gives the following differences for the three 

 years 1837 to 1840:— 



Declination, 8 a.m. 



April 



May 



June 



July 



August ... 

 September 

 October ... 

 November 

 December 

 January ... 

 February . . , 

 March 



Declination, 1 p.m. 



Fourth Year, 



+ 4 32-2 

 + 2 25-2 

 + 2 14-8 

 + 45-4 

 + 1 41-9 

 + 1 09-1 

 4- 50-2 



- 2 57-2 



- 4 55-5 



- 2 33-8 



- 2 32-2 



- 40-4 



+ 4 20-6 



+ 4 10-0 



+ 3 30-1 



+ 2 12-1 



+ 3 23-3 



+ 1 41-4 



- 47-8 

 -3 21-7 

 -5 171 



- 4 010 



- 4 06-3 



- 1 43-7 



+ 3 08-9 

 + 2 40-4 

 + 1 40-9 

 + 2 42-0 

 + 4 32-4 

 + 1 51-9 

 + 18-4 



- 2 25-7 



- 4 320 



- 4 460 



- 3 187 



- 1 52-4 



+ 4 00-6 

 -I- 3 05-2 

 + 2 28-6 

 + 1 53-2 

 + 3 12-5 

 + 1 34-1 

 + 06-9 



- 2 54-9 



- 4 54-9 



- 3 46-9 



- 3 191 



- 1 25-5 



The numbers in the last column are still charged with the 

 secular change, from which we may free them by reducing 



