122 Prof. Hansteen on the Number and Situation 
rinenburg during the same period is = 4° 37’, or 63 per 
annum; in Tobolsk = 3° 23/, or. = 46 per annum; in 
Jakutskoi, from 1768 to 1788, = 3° 15', or-= 9'"7 per ann. 
Thence we find by interpolation, that in 1770 the declination 
in Jakutskoi was = 4° 50! W., in Tobolsk = 4° 27! E., and 
at Barnaul 2° 45!.. If we pair these declinations in the usual 
manner, we find the situation of the point in 1770: 
According to the Observations Distance from | Longit. from 
the Poles. Ferro. 
— | 
In Tobolsk and Jakutskoi 4 
In Barnaul and Jakutskoi 4. 
i ° U 
4 117 31 
4 
2 120 48 
Mean... 4 14* {119° 9! 30" 
If we compare with this the above result for the year 18035, 
we find the distance from the pole to have remained nearly 
the same, but that the longitude of this point increased from 
1770 to 1805; the change during these 35 years having 
been = 133° 49! — 119° 9! 30" = 14° 39' 30", or 25/128 per 
annum. Thus this magnetic pole has a motion from west to 
east. Whether its course be a circle round the terrestrial pole, 
or a differently curved line, or whether it be merely an oscil- 
lation, must be learned from the experience of future ages. 
If we assume a uniformly circular motion, the period of the 
revolution, according to the degree of velocity found above, 
would be 860 years. 
Whether the magnetic point of convergence found above in 
North America be also moveable, must be determined by cal- 
culating its position from older observations, and comparing 
it with that of the year 1769. 
The following observations of declinations, made at the Fort 
Prince of Wales, distinctly show that this point has a percep- 
tible motion towards the east: 
By Chr. Middleton in 1725=21° 0! W. | annual change. 
wed ae See 1738=18 0O 13/9 
we? eal Bas eel e177 150°. 
By W. Wales ... 1769= 9 41 163 
1798=1 0E. | 221 
1813= 6 OF. | port 
From 
* Tn the original, as well as in the work on the magnetism of the earth, 
p. 94, it is stated by mistake at 4° 17’ instead of 4° 14’. 
+ These two observations are from the MS. journal, entitled His Majesty’s 
sloop 
