17B SIEGE OF TEIE SOUTH POLE 
seventeenth century being right enough in symbolising 
fidelity by the true-pointing compass— but year by year 
the declination continued to increase, this time toward 
the west, until in 1815 it came to a maximum of 24^° 
West of North, the compass needle actually pointing 
N.W. by N f N. Since that time it has been steadily 
returning toward true north. These were facts so prom- 
inent that the roughest observations served to make them 
plain. It was only when the scattered data were col- 
lected and critically compared that the difficulty of arriv- 
ing at a general statement became obvious. 
The astronomer Halley it will be remembered had 
taken command of a ship of war in 1700, when he con- 
ducted the first scientific expedition under the British or 
any other flag to study magnetic declination in the 
North and South Atlantic. The result was to enable 
him to produce the first magnetic chart on which he had 
the happy inspiration to draw curves connecting all 
places where the magnetic declination had equal values. 
This was the first use of that invaluable cartographical 
method of contour lines which has since proved, one 
might almost say, the foundation of the science of 
geographical distribution, for it enables all phenomena, 
visible or invisible, to be represented on maps if they are 
capable of being measured and expressed in figures. 
Following Halley’s advice ship-masters continued to 
note the variation of their compasses from time to time 
and to place their results on record, but for more than 
half a century these results were so chaotic as to be 
practically valueless. Then Captain Flinders discovered 
that the iron of a ship affected the compasses in a different 
way when the ship s head pointed in different directions, 
so that a great part of the observed variation was simply 
