ii9 
in the direction of the compass needles , &c. 
observation in every ship as soon as the distribution of iron is 
completed, may therefore be considered as confirmed by the 
observations in the Isabella and Alexander ; whilst his rule 
of proportion may receive a verbal alteration to render it 
more suitable for general application : so corrected, it would 
be as follows. The expressions substituted being marked in 
italics, and the original words entered in the margin. 
“ The error produced in any direction of the 
ship's head, will be to the error at the point of 
East or west. the greatest irregularity , as the sine of the angle 
between the ship’s head and the points of no 
Magnetic meridian, error to the sine of eight points or radius.” 
Thirdly; Capt. Flinders’s experience in the Investigator 
showed that the maximum of error in the same compass, 
would be different in different parts of the world, although 
the use of the compass was confined to one particular spot in 
the ship, and every precaution taken to avoid an interference 
with the distribution of the ship’s iron. 
It is worthy of remark, that by multiplying observations 
and by comparing the series one with another, he was thus 
practically led to trace a connection between the amount of 
the errors and the dip of the needle; a knowledge of the fact 
preceding, in his mind, any theoretic suggestion that such 
might be the case. 
It does not appear indeed that the principal cause of this 
connection was even subsequently known to him; he per- 
ceived that the influence of local attraction on the compass 
needle increased as the # dip became greater. He endeavoured 
to account for this circumstance, on a supposition that all iron 
