APPENDIX. 



The obfervations on the dip of the needle, during this 

 voyage, were made with great care : firft the dip was ob- 

 ferved with the divided arch to the Eaft, the inftrument 

 being placed as near as pollible in the magnetic meridian ; 

 it was then turned, and the obfervation made with 

 the divided arch to the Weft : the poles being changed, 

 the obfervation was repeated in the fame manner. The 

 a6lual obfervations are exprefled in the fecond, third, 

 fourth, and fifth columns ; and the mean refult in the 

 fixth. It appears by thefe obfervations that the dip in- 

 creafes in going North. 



There is no reafon at prefent to fuppofe that the dip is 

 liable to any variation in the fame place at different periods 

 of time, it having been obferved in London by Norman, 

 who firft difcovered it in 1592, to be 71° 50'; and by 

 Mr. Nairne, in 1772, about 72°. The difference 

 between thefe obfervations, taken at fuch diftant 

 periods, is fmaller than that found between feveral of 

 Mr. Nairne's obfervations compared with each other; 

 and therefore we have no reafon to conclude that the dip 

 has altered fince Norman's time : the care with which his 

 inftrument was conftruded, and his obfervations made, 

 leaves no room to doubt of their accuracy. 



121 



TABLE 



