Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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realis. The gentle flashes and streamers of auroral light, he
thinks, are caused by the passage of unusual quantities of elec-
tricity from the regions above, to the negative pole of the earth.
But that this is also connected with the magnetism of the earth,
is quite as evident from the fact that the magnetic needle is found
to be more or less affected by the north, or perhaps the south
currents,during these gorgeous dissolving views of auroral exhi-
bition. The irregular and augmented action of the electro-mag-
netic telegraph during some days, causes registers to operate
as if in contact with a powerful battery, and thus gives the
signal of this as yet unseen, but felt, atmospheric phenomenon,
which is usually verified in the evening by the appearance of
the halo and streamers of an aurora borealis.
This is admirably demonstrated by causing one of the poles of
a straight magnet, that connects with the moist earth, to enter
the glass globe of an air-pump. Above and around the upper
end of this magnet is placed a metallic circle. Now, upon
removing the air from the globe, and charging the circle with
the electric machine, there appear the halo of dim light and
the streamers of a miniature aurora.
Meteorology.
It is profitable and interesting to know in this connection, that
Meteorological observations have now become multitudinous.
These, conducted by so many scientific persons, and in so great
a number of countries, as well as under so great a variety of
circumstances, and that for so many successive years, appear to
us calculated to inspire the greatest confidence, so far as the
facts are agreed upon. The following table, formed by the dis-
tinguished De la Rive in 1858, has made manifest the following
concise results: —
1. Whatever the state of the sky may be, the electricity of the
air presents a maximum or greatest tension in January, and
a minimum or least tension towards the summer solstice.
2. The difference between the maximum and the minimum is
much more sensible during serene weather, than it is during
cloudy weather.