36 JOURNEY TO THE SHORES
About half a mile from the bend or knee of the lake, there is a
small rocky islet, composed of magnetic iron ore, which affects the
magnetic needle at a considerable distance. Having received previous
information respecting this circumstance, we watched our
compasses carefully, and perceived that they were affected at the
distance of three hundred yards, both on the approach to and departure
from the rock: on decreasing the distance, they became
gradually more and more unsteady, and on landing they were
rendered quite useless ; and it was evident that the general magnetic
influence was totally overpowered by the local attraction of the ore.
When Kater’s compass was held near to the ground on the N.W.
side of the island, the needle dipped so much that the card could not
be made to traverse by any adjustment of the hand ; but on moving
the same compass about thirty yards to the west part of the islet, the
needle became horizontal, traversed freely, and pointed to the
magnetic north. The dipping needle being landed on the S.W.
point of the islet, was adjusted as nearly as possible on the magnetic
meridian by the sun’s bearings, and found to vibrate freely, when the
face of the instrument was directed to the east or west. The mean
dip it gave was 80° 37' 50". When the instrument was removed
from the N.W. to the S.E. point, about twenty yards distant, and
placed on the meridian, the needle ceased to traverse, but remained
steady at an angle of 60°. On changing the face of the instrument,
so as to give a S.E. and N.W. direction to the needle, it hung vertically.
The position of the slaty strata of the magnetic ore is also
vertical. Their direction is extremely irregular, being much contorted.
Knee Lake towards its upper end becomes narrower, and its rocky
shores are broken into conical and rounded eminences, destitute of
soil, and of course devoid of trees. We slept at the western extremity
of the lake, having come during the day nineteen miles and a half
on a S.W. course.
We began the ascent of Trout River early in the morning of the