Observations of Auroræ on August 12 and 13

Abstract

THE finest display was between 10 and 11 o'clock on the evening of the 12th, when a magnificent corona was formed almost exactly on γ Cygni. At this time the bases of the columns on the eastern horizon were distinctly red. Unfortunately the spectroscope could not be brought to bear until the aurora had faded to a small fraction of its greatest brightness. With a very small dispersion (Vogel spectroscope) the spectrum was continuous from W.L. 557 mm. to W.L. 473, with strong traces of a finely banded spectrum, terminating abruptly at the great line 557. Towards the violet an isolated line was seen and measured.