APPENDIX. 149 



In the present instance the observed dip is 86° 32' ; now 

 nat. tan. 86° 32' is 16.507456, therefore ^ tan. 86° 52' := 

 8.253728 = tan. 83° 6' =r arc mZ, or magnetic latitude of 

 Seahorse Point ; and, consequently, ttZ, or the co-latitude, is 

 6° 54/ ; which is the distance of the place of observation, 

 measured on the arc of a great circle, from the magnetic 

 pole. 



Now, then, in the spherical triangle ttPZ there are 

 given, the arc ttZ :==. 6° 54', the magnetic co-latitude ; the 

 arc PZ = 2G° 33', (rejecting the seconds,) the terrestrial 

 co-latitude, and the angle ttZP, s: 37° 30', the variation ; 

 to find the angle ttPZ, or the difference of longitude be- 

 tween the two meridians, and ttP, the co-latitude of the 

 magnetic pole. 



The actual solution of this problem gives the angle ttPZ 

 == 11° 32', the difference of longitude, which added to the 

 longitude of the place 80° 51', gives 92° 32' W., for the 

 longitude of the magnetic pole reckoned from London ; and 

 the arc -tj-P == 21° 27', which deducted from 90° leaves 

 6S° 33' for the latitude of the pole. It is unfortunate that 

 no other opportunity occurred during the voyage of making 

 a similar shore observation ; but it is, at the same time, 

 highly satisfactory, that the resulting place of the pole, as 

 deduced above, agrees Mathin certain narrow limits with the 

 places of the sam.e as obtained from the observations made 

 in the several voyages of Captains Ross and Parry, and 

 with those made by Captain Franklin in his over-land 

 journey. These all give for the place of the pole a latitude 

 not differing greatly from 70°, and a longitude a little more 

 or less than 100° ; but still there is a certain discrepancy, 

 which is more and more obvious as the latitude diminishes, 

 and which shows that the m.ore northerly and westerly the 

 place of observation is, the greater is the deduced western 



