130 
A VOYAGE TO 
[South Coast. 
1802. for sailneedIes,marlinespikes,or other implements ofiron which might 
ThSsdayis. have been left in or about the binnacle, but I could fix on nothing 
unless it were the guns ; for it is to be observed, that notwithstanding 
the constancy of the differences, the idea of any regularly acting 
cause to derange the needle had not yet fixed itself in my mind. 
The perfection to which naval science had arrived did not allow me to 
suppose, that if a constant and unavoidable attraction existed in ships, 
it would not have been found out, and its laws ascertained ; yet no 
longer than three days before, differences had been observed, sufficient 
one would think to have convinced any man that they were produced 
by some regular cause. Off Point Drummond, about fifteen leagues 
to the north of where the variation i° 39' east was observed with the 
ship's head at south, both azimuths and an amplitude had been taken 
with the same compass. The first gave i° 33' west, the head being 
south-east-by-east; and after we had tacked, and the head was 
south-west-by-west, the amplitude gave 3 0 56' east ! I did not yet see, 
that as the ship's head was as much on the east side of the magnetic 
meridian in one case, as it was to the west in the other, so was the 
variation as much too far west then, as it was too far east afterward. 
Differences like this, of 5^ °, which had frequently occurred, seemed 
to make accuracy in my survey unattainable, from not knowing what 
variation to allow on the several bearings. The guns were removed 
in the hope to do away the differences, but they still continued to 
exist, nearly in the same proportion as before ; and, almost in despair, 
I at length set about a close examination of all the circumstances 
connected with them, in order to ascertain the cause, and if possible 
to apply a remedy ; but it was long, and not without an accumula- 
tion of facts, before I could arrive at the conclusions deduced and 
explained in the Appendix No. II. to the second volume. 
We tacked towards the land soon after noon; and being 
within five miles of it at three o'clock, stood off again. The fur- 
thest extreme of the main land was a sloping low point, distant 
about three leagues ; but two or three miles beyond it, to the south., 
