APPENDIX. 



THE great interest which naturally attaches to compass 

 observations, made in the focus of magnetic action, to which 

 the Griper advanced in her recent voyage, renders it desir- 

 able that the results obtained should be properly analyzed, 

 in order to ascertain whether the curious phenomena which 

 the needle presented were such as to throw any new light 

 upon the mysterious action of terrestrial magnetism ; or 

 whether they will serve in any way to confirm the theory 

 of this action at present most generally admitted. 



The first and most important question in all cases of this 

 kind is, to determine the situation of the magnetic pole, if 

 there really be such a pole ; and if not, at least to ascertain 

 the point respected as such, by a needle in any particular 

 place. There are two ways in which this may be effected ; 

 the first is by producing any two magnetic meridians, till 

 they intersect each other, which intersection will, of course, 

 be the common pole of the two places ; and the second is by 

 means of the relation theoretically established between the 

 dip and variation in any one given place, which latter, as 

 being the most independent, is to be preferred when it can 

 be had recourse to. 



