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576 SWEDENBORG AS A MAN OF SCIENCE. [Doc. 200 .
minutes to six hours; and in one and the same observation
the difference may amount to eight minutes, or range between
45’ to 53’, of which the Professor has taken the mean, viz.
forty -nine minutes as indicating the true declination, (see
Transactions of the Academy, p. 387.) For if the least ex
halation of iron be conveyed by the air or wind, it would
penetrate without the least obstruction through glass, yea even
through metals, such as gold and silver, and through water
and fire, and according to observations instituted by many,
this would cause a deviation of from thirty or forty minutes
and upwards in a compass the graduated circle of which is
small, and where the needle is placed at some distance above
it. This may also be concluded from the fact that frequently
a very great difference is noticed between the observations
made with one compass at several places, or with several
compasses at one place ; whence some have been led to attri
bute the fault not to themselves, but to the supposed incon
stancy of the declination in one and the same place, and at
one and the same time. Nevertheless, the eastern and western
longitude may be obtained by taking the mean of several ob
servations.
The fact of the deviation of the needle having its even and
constant motion and orbit appears very clearly from the nu
merous observations instituted during a whole century at Paris,
London, and other places ; the difference or progress between
them, from year to year, has shown itself so even that scarce
ly any increase is noticed in the course of one year compared
with that of another, while yet the magnet at the same time
continues to decline until it reaches its highest point, when it
begins to turn about in the opposite direction. According to
my computations this is not likely to happen in Paris for
forty years to come. It is also remarkable that when the
magnet is found to be stationary for a year, the very
next year the declination is found to have progressed and in
creased at such a rate, that the deficiency of the one is com
pensated by the year following ; whence it appears very
clearly that the magnet has not stood still, and that the
error has not been due to the magnet, but to the ob
server. Indeed, over the whole globe the declination of the
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