142 Capt. Sabine’s observations on the magnetic needle. 
Should the amount of this change be considerably augmented 
in high magnetic latitudes, careful observations on the direc- 
tion of the needle at different hours of the day, on all conve- 
nient occasions, might be serviceable towards a more certain 
knowledge of its causes, than has been hitherto obtained from 
observations made where the effects are so inconsiderable. 
The influence of the ship’s iron on their compasses increas- 
ing, as the directive power of magnetism diminished, produced 
irregularities that rendered observations on board ship of little 
or no value towards a knowledge of the true variation ; a few 
azimuths which were observed in the Isabella, have been 
selected for the purpose of exemplifying this remark. They 
will also show, how essential it is to navigation in high lati- 
tudes, that the nature of the errors which the ship’s attraction 
produces in her compasses, should be understood. 
