ii 6 Capt. Sabine on irregularities observed 
from the deck. The elevation was an advantage to the com- 
pass in such high magnetic latitudes, by rendering it less 
liable to accidental disturbance, on the removal of such im- 
plements of iron as were required to be kept on deck for use. 
The Alexander not having a similar cross beam, her compass 
was fixed amidships on a box of sand placed on the com- 
panion, between five and six feet above the deck. 
Secondly; Captain Flinders found that in his compass 
permanently fixed as described, no error took place when 
the ship’s head was on the magnetic north or south points ; 
showing, that at such times the attraction of the ship, and of 
magnetism, were in the same line of direction. The maximum 
of error also took place when the ship’s head was at right- 
angles to these points ; namely, at east or west ; being how- 
ever in opposite directions, in excess of the true variation on 
the one side, and in defect on the other ; so that the extreme 
difference occasioned by altering the course from east to west 
or the reverse, would be twice the error at either. 
On the intermediate points, the ratio of the error to its 
maximum was as the “ sine of the angle between the ship’s 
head and the magnetic meridian to the sine of eight points or 
radius,” or sufficiently near to admit of corrections being 
calculated for every course, when the error on a single one 
was known by observation. 
Thus far the experiments which Captain Flinders tried in 
every ship corresponded, excepting only that the maximum of 
error in different ships at the same place would differ materially. 
The accordance in so many ships gave him reason to 
believe that in compasses placed near the binnacle, and 
amidships, the points of no error would be most commonly 
