Capt. Sabine on irregularities , &c. 113 
unsuspected, whilst its effects had produced a general impres- 
sion, that the azimuth compass was in itself an imperfect 
instrument, and only to be relied on within certain undefined 
and variable limits. 
It was reserved to the accurate observation, and the habit 
of recording and comparing apparently trivial and accidental 
differences in results, which distinguished the late Mr. Wales 
(astronomer in the second voyage of Captain Cook,) to enable 
him to lead the way to a knowledge of the nature and causes 
of these errors ; he remarks, “ that in the passage of the 
Resolution and Adventure to the Cape of Good Hope, and 
subsequently, the greatest west variations had happened when 
the ship’s head was north and easterly, and the least when it 
was south and westerly, differing very materially from one 
another with the ship’s head in different positions, and still 
more when observed in different ships thus manifesting 
that they were something more than accidental. 
This voyage was the last in which Mr. Wales embarked, 
and the investigation does not appear to have been pursued in 
this country until the voyage of discovery to Terra Australis, 
in the first years of the present century. The survey of the 
coast of New Holland being carried on in a considerable mea- 
sure, by the intersection of compass bearings taken from the 
deck of the Investigator, so much embarrassment and per= 
plexity were found to arise from the effects of local attraction, 
that much of Captain Flinders’s attention and thoughts were 
necessarily devoted, to a consideration of some means of reme- 
dying the inconvenience. 
On his return to England, he obtained permission from the 
Lords Commissioners of the Admiralty to make a course of 
mdcccxix. O 
