In the voyage of the ‘Hansa’ (‘Recent Polar Voyages,’ p. 420), on the 9th September, 1869, at 10 P.M., Aurora gleams appeared in the west, shooting towards the south. “Radiant sheaves and phosphorescent bands mounted towards the zenith,” but the phantasmagoria quickly vanished. M. Silbermann (‘Comptes Rendus,’ lxviii. p. 1120) mentions storm-clouds which threw out tufts of cirri from their tops, which extended over the sky, and resolved into, first, fine, and afterwards more abundant rain. (I saw a fine day example of this on the Lago di Guarda, ending in a copious discharge of rain attended with loud thunder and vivid lightning.) Usually the fibres were sinuous; but in much rarer cases they became perfectly rectilinear and surrounded the cloud like a glory, and occasionally shone with a sort of phosphorescence. On the night of 6th September, 1865, at 11 P.M., a stormy cloud was observed in the N.N.W., and lightning was seen in the dark cumulous mass. Around this mass extended glories of a phosphorescent whiteness, which melted away into the darkness of the starry sky. Round the cloud was a corona, and outside this two fainter coronæ. After the cloud had sunk below the horizon the glories were still visible.
Sabine’s luminous cloud at Loch Scavaig, Skye. Other observations of luminous clouds.
Sabine mentions a cloud frequently enveloping Loch Scavaig, in Skye, as being at night perfectly self-luminous, and that he saw rays, similar to those of the Aurora, but produced in the cloud itself. Sabine also refers to luminous clouds mentioned in Gilbert’s Annals, and to observations by Beccaria, Deluc, the Abbé Rozier, Nicholson, and Colla; and to luminous mists as observed by Dr. Verdeil at Lausanne in 1753, and by Dr. Robinson in Ireland.
Aurora at Melville Island.
He also describes (Parry’s First Voyage) an Aurora seen at Melville Island, and says the light was estimated as equal to that of the moon when a week old. Besides the pale light, which resembled the combustion of phosphorus, a slight tinge of red was noticed when the Aurora was most vivid; but no other colours. This Aurora was repeatedly seen on the following day.
Procter suspects Aurora is formed in a mist. M’Clintock: Aurora is never visible in a perfectly clear atmosphere.
Mr Procter, in a letter to me, suspects that the Aurora is generally formed in a sort of “mist or imperfect vapour;” and this mist or imperfect vapour seems in many instances to form part of the Aurora, and to partake of its self-luminous character. M’Clintock does not imagine that the Aurora is ever visible in a perfectly clear atmosphere. He has often observed it just silvering or rendering luminous the upper edge of low fog or cloud-banks, and with a few vertical rays feebly vibrating.
Aurora of Feb. 4, 1874. Illuminated fog-cloud. Capt. Oliver’s meteor-cloud. Auroral display, 24th Oct., 1870. Streamers of phosphorescent cloud.
An instance of apparent phosphorescence is supplied by the Aurora of the 4th February, 1874 (antè), when a bright cloud of light was seen which gave the impression of an “illuminated fog-cloud.” Captain S. P. Oliver saw at Buncrana, Co. Donegal, on February 4, 1874, what he describes as a meteor-cloud, viz. “a broad band of silvery white and luminous cloud.” This appearance, as described by another correspondent, was evidently an imperfectly formed (perhaps actually forming) Auroral arc. The great Auroral display of the 24th of October, 1870, as seen by me, included, according to my notes made at the time, “streamers of opaque white phosphorescent cloud, very different from the more common transparent Auroral diverging streams of light.”