in the direction of the compass needles , &c. 121 
the error, in the one ascertained instance, may have borne to 
the dip. 
In the observations made in the Isabella at Shetland, where 
the dip is 74 0 2i-§', the maximum of error was 5 0 34' easterly 
of the true variation, with the ship's head at E. S. E. and 5 0 
46' westerly at W. N.W. making an extreme difference of 
1 1° 20'. 
By Captain Flinders's rule, the common multiplier for this 
compass would have been about one twelfth, or .083, which 
at a dip of 86° of, which was the greatest observed during 
the late voyage, would have given an error of between 7 0 and 
8°, making the extreme difference 15 0 ; whereas repeated 
observation showed it to be at that time more nearly 50°, if 
not exceeding that amount. 
The inadequacy of the rule will also appear by reference 
to the observations made by the Alexander in Baffin's Bay. 
The error at eight points being 6° 46', at a dip of 84° 30'; it 
ought scarcely to have exceeded 7 0 at the greatest possible 
dip, making an extreme difference of less than 15 0 . No op- 
portunity occurred indeed of making accurate observations 
at a greater dip than the above ; but the difference in the 
bearing of objects before and after tacking indicated with 
sufficient certainty, that the error had increased to an amount 
very far beyond 15 0 ; frequent instances of an extreme diffe- 
rence of from 3 to 4 points being remarked, as the ship 
approached the farthest western longitude to which she 
attained in a high latitude ; this was in Lancaster's Sound of 
Baffin, into which inlet the expedition sailed beyond the 8i° 
of west longitude in the parallel of 74 0 and a few minutes. 
It is much to be regretted that the service did not admit an 
opportunity to be afforded, of making observations on the 
mdcccxix. R 
