GAUSS AND WEBER ON TERRESTRIAL MAGNETISM. 55 



clination at the same hour. In order to be able to calculate 

 more easily on the possibility of a long and continuous perseve- 

 rance, by which alone labours of this kind can be of value, I 

 have at first rather chosen a limited plan than attempted to 

 combine too much at once. On this account only two observa- 

 tions are made daily ; at eight in the forenoon, and one in the 

 afternoon, according to mean time. These hours, which were 

 most easily compatible with other duties, are also suitable 

 ones, because in the regular coui'se of the magnetic movements 

 the position of the needle at 1, p.m. is never far from the maxi- 

 mum of declination, and during the greatest part of the year, the 

 hour of minimum is not far from 8, a.m. Observations at fixed 

 hours of apparent solar time would, it is true, have been more in 

 accordance with nature ; but the much greater facility of an ar- 

 rangement made according to mean time, renders it deserving 

 of preference in this case, where the chief point is to secui'c a per- 

 severing continuance in one and the same principle. 



A regular register was commenced on the 1st of January, 1834 ; 

 but the first two months and a half have been omitted in the 

 folloA\ing extract, because during that time it was frequently 

 necessaiy to wind up the suspension -thread, whereby changes 

 were produced in the torsion which were at first not sufficiently 

 attended to. From the l7th of March a stronger suspension- 

 thread was employed, consisting of 200 fibres, of which the point 

 of no-torsion had been previously accurately determined ; when- 

 ever changes were subsequently made in respect to the thread, 

 or to any other circumstance connected with the elements of 

 reduction, the necessary corrections, or modifications of those 

 elements, have each time been applied. During the first months 

 various sufficiently practised observers took part with me in the 

 observations ; but since the 1st of October, 1834, they have been 

 regularly made by Dr. Goldschmidt, his place having been only 

 occasionally supplied, when necessary, by other expert observers. 

 I have already communicated in the Gottingen Gelehrten 

 Anzeigen, 1834, p. 1269, and 1835, p. 345, the monthly means 

 deduced from these determinations up to January, 1835: they 

 are now given for three entire years. 



