ig 6 Mr. Flinders on certain Differences 
inclination of the south end of the dipping needle 50° 50', the 
needle stood vertical when the face of the instrument was 
S 2 0 E, I then took the following bearings : Extensive Mount 
108° 30b the same exactly as by back bearing. Double Peak 
1 43°3° / ; from hence I rowed round the Head, and landed 
on a rock, whence the top of the hill bore SSW one-sixth of 
a mile ; Extensive Mount bore no 0 14', the inclination of the 
dipping-needle 50° 29b and the needle stood vertical when 
the instrument faced S 3 0 E. Thus the difference was i^° in 
the horizontal, and in the vertical direction of the needle. 
Ascending the hill, I made the following observations on the 
top: Extensive Mount 113 0 50b a, island 133 0 52b Double 
Peak 148° 32'; the inclination of the needle was 53 0 20', and 
it stood vertical at S 3 0 E. The differences here are 5 0 io 7 in 
the horizontal, and 2 0 30' in the vertical direction, from what 
the needle stood at in the first morning's place. On moving 
ten yards SSE, the bearings were, Extensive Mount 108° 44b 
Double Peak 143 0 25'; the inclination was 52 0 i8 7 , and the 
needle was vertical when the instrument faced S 5 0 W. In this 
4th set of observations, the horizontal direction of the needle 
is only a few minutes different from the first place, but the 
vertical direction is T 28'. From the top of the hill I now 
moved twenty yards to the north-eastward, when Extensive 
Mount bore 110 0 , Double Peak 144 6 42 7 ; the inclination of the 
dipping needle was now 50° 35b and it stood vertical at S 3 0 W. 
Thus it appears that the polarity of the magnetic needle is 
most interrupted at the top of the hill, both according to 
the theodolite and dipping-needle. Whether this may arise 
from some particular magnetic substance lodged in the heart 
of the hill, or from the attractive powers of all the substances 
