Auroræ: Their Characters and SpectraCapron, J. Rand
History
Auroræ: Their Characters and Spectra
Capron, J. Rand
Auroras
The infrequency of Auroræ during the years 1876-78, and a corresponding
comparative absence of sun-spots, may be added to the evidence on the
subject. I have seen no account of important Auroræ during the years
mentioned, and day after day has recently (1878) passed with a perfectly
clean sun-disk.
_Aurora and Electricity._
[Sidenote: Aurora and electricity. Sir John Franklin’s experience with
electrometer.]
Sir John Franklin failed to get indications of electricity connected
with the Aurora with a pith-ball electrometer; but with another form of
electrometer specially constructed for the purpose he seems to have got
some, though not very strong or regular, indications of repulsion between
the needle of the instrument and the conductor when Auroræ were seen. He
does not decide whether the electricity was received from or summoned
into action by the Aurora.
[Sidenote: Parry’s experience.]
Parry, at Fort Bowen, with a gold leaf electroscope connected with a
chain attached by glass rods to the skysail mast-head, 115 feet above
sea-level, found no effect.
[Sidenote: Dr. Allnatt’s experience, February 4, 1872.]
Dr. Allnatt, at Frant, during the display of 4th February, 1872,
found the earth’s electricity so powerful that the gold leaves of the
electrometer remained divergent for a considerable time.
[Sidenote: M’Clintock found electroscope affected in Baffin’s Bay and
Port Kennedy.]
M’Clintock observes that on six occasions of Aurora in Baffin’s Bay, the
electroscope was strongly affected, and on three occasions of Aurora at
Port Kennedy. The electricity was always positive.
Dec. 18.—Dr. Walker called him to see the electroscope. The charge was at
first weak, but afterwards strong enough to keep the leaves diverged. Dr.
Walker found two periods of minimum electrical disturbance about 9 P.M.
and noon.
[Sidenote: Electric currents in telegraphic wires during Auroræ.]
Electric currents have been reported as produced in telegraph wires
during Auroræ. Though transient they are said to be often very powerful,
and to interrupt the ordinary signals. Loomis (Sillim. Journ. vol.
xxxii.) mentions cases where wires have been ignited, brilliant flashes
produced, and combustible materials kindled by their discharge.
Here, too, we may note the account of electric phenomena in the case of
the Aurora Australis described (_antè_, p. 28) by Mr. Proctor.
[Sidenote: Mr. George Draper’s report as to disturbed condition of the
Indian Submarine and other cables during Aurora of February 4, 1872.]
Public-domain text, read in full here on John Shaqi.
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