Light Science for Leisure Hours: A series of familiar essays on scientific subjects, natural phenomena, &c.Proctor, Richard A. (Richard Anthony)
Science
Light Science for Leisure Hours: A series of familiar essays on scientific subjects, natural phenomena, &c.
Proctor, Richard A. (Richard Anthony)
Science
We find, first, that the world may be divided into two unequal
portions, over one of which the needle has a westerly, and over the
other an easterly, declination. Along the boundary line, of course, the
needle points due north. England is situated in the region of westerly
magnets. This region includes all Europe, except the north-eastern
parts of Russia; Turkey, Arabia, and the whole of Africa; the greater
part of the Indian Ocean, and the western parts of Australia; nearly
the whole of the Atlantic Ocean; Greenland, the eastern parts of
Canada, and a small slice from the north-eastern part of Brazil. All
these form one region of westerly declination; but, singularly enough,
there lies in the very heart of the remaining and larger region of
easterly magnets an oval space of a contrary character. This space
includes the Japanese Islands, Manchouria, and the eastern parts of
China. It is very noteworthy also, that in the westerly region the
declination is much greater than in the easterly. Over the whole
of Asia, for instance, the needle points almost due north. On the
contrary, in the north of Greenland and of Baffin’s Bay, the magnetic
needle points due west; while still further to the north (a little
westerly), we find the needle pointing with its north end directly
towards the south.
In the presence of these peculiarities, it would be pleasant to
speculate. We might imagine the existence of powerfully magnetic
_veins_ in the earth’s solid mass, coercing the magnetic needle from a
full obedience to the true polar summons. Or the comparative effects of
oceans and of continents might be called into play. But unfortunately
for all this, we have to reconcile views founded on _fixed_ relations
presented by the earth with the process of _change_ indicated above.
Let us consider the declination in England alone.
Public-domain text, read in full here on John Shaqi.
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