118 Prof. Hansteen on the Number and Situation 
east to west by the Atlantic Ocean to Greenland, it increases 
in proportion as we approach the southernmost points of 
that country. Thus it is at St. Petersburg about = 8° W., 
at Stockholm = 152°, in Christiania = 20°, in London = 
242°, on the north coast of Iceland above 40°, and in the co- 
lony of Godthaab in Greenland above 51°. From the western 
coast of Greenland to Hudson’s Bay it decreases again by some 
degrees: but in Hudson’s Bay this decrease is so strong, that 
in the year 1769 it was found in fort Prince of Wales, on 
the western coast of the bay, to have been only = 9°41’. If 
we proceed on the continent, it disappears entirely, becomes 
then easterly, and increases so rapidly towards the western 
coast of America, that it was, according to the observation of 
Cook in the year 1778, in Nootka Sound = 19° 51’ E.; and in 
the same year, in the northernmost part of Behring’s Straits, 
= 35° 37/E. If we extend the arrows in Nootka Sound and in 
Hudson’s Bay and Strait, we see them meet in one point, 
which is about 20° distant from the pole, and about 259° east 
of Greenwich. 
__ In fact, every apparently straight line on the surface of the 
earth is the arc of a great circle. If, then, we wish todetermine 
the situation of this point more accurately, we must combine 
some of the above-mentioned points of declination, two by two, 
(for instance, in Nootka Sound and in fort Prince of Wales), and 
calculating, according to therules of spherical trigonometry, the 
situation of the point of meeting of these prolonged lines .of 
magnetical direction (the magnetical point of convergence), we 
shall obtain as many determinations of the same as we have 
pairs of observations. In order to obtain the situation of this 
point, I have made use of the following observations : 
West 
Toa Place of Ob- : North | Long. |Declin. 
Observer. servation, Time. Lat. | from | West. Nos, 
Lond. 
fe 1774. July 23|62 3/69 0/43 6/1 
7 . July 23 | 62 
here — 27/62 23/71 30| 42 50| 2 
Sie eee — 98/62 25/71 30/44 0} 3 
Hudson’s Bay Aug.14 | 56 53|85 22/28 0O| 4 
Fort Moose | Sept. 8/51 20) 82 30/17 0} 5 
||Fort Albany — 14| 52 22|)82 30)17 0/6 
W. Wales |Ft. Pr.of Wales |1769. — —|58 47/94 4} 9 41) 7 
Among these observations the 7th can be most relied upon, 
having been made on shore by the astronomer Wales, by 
means of a large compass and an exact meridian, and being 
the 
