GREEN SUN AND STRANGE SUNSETS.
During the first half of September, the sun in Ceylon and India, and also in the West Indies, presented at rising and setting the appearance of a green or greenish-blue disc. Even when at his highest the sun appeared pale blue in Ceylon (from the other places no account of the sun’s aspect at high noon has reached me). On September 2, at Trinidad, the sun looked like a blue globe after five in the evening, “and after dark,” says the report, “we thought there was a fire in the town, from the bright redness of the heavens.” At Ongole, as the sun approached the horizon, his disc passed from a bluish tinge to green, which became tinged with yellow as he approached the horizon. “After he had set, light yellow and orange appeared in the west, a very deep red remaining for more than an hour after sunset; whereas, under ordinary conditions, all traces of color leave the sky in this latitude,” says the narrator, “within half an hour after the sun disappears.” These accounts, from both the eastern and western hemispheres, seem clearly to associate the green sun which attracted so much attention in the tropics early in September, with the remarkable sunsets seen in Arabia, in Africa (North and South), and throughout Europe during October and November. For we see that whatever may have been the explanation of the green sun, the phenomenon must have been produced by some cause capable of producing after sunset a brilliant red and orange glow, for a time much exceeding the usual duration of the twilight afterglow. The occurrence of the afterglow, with the same remarkable tints and similar exceptional duration elsewhere—though some weeks later—shows that a similar cause was at work.
Two points are clear. First, the cause alike of the greenness of the sun and the ruddy afterglow was in the air, not outside; and, secondly, the matter, whatever it was, which made the sun look green when he was seen through it, and which under his rays looked red, was high above the surface of the earth. It can readily be shown, so far as this last point is concerned, that matter at a lower level than sixteen miles could not have caught the sun’s rays so long after sunset as the glow was seen. On the other point it suffices, of course, to note that if some cause in the sun himself had been at work, the whole earth would have seen the green sun, while the afterglow would have found no explanation at all.
As to the actual cause to which both phenomena are to be ascribed, we must, I think, exculpate Krakatoa from all part or share in producing these strange effects. The appearance of a blue sun at Trinidad, followed two or three days later by a green sun in the East Indies, can not possibly be associated with the occurrence of an earthquake on the Javan shore a few days earlier. Beside, it must be remembered that we should have to explain two incongruous circumstances; first, how the exceedingly fine matter ejected from Krakatoa could have so quickly reached the enormous height at which the matter actually producing the afterglow certainly was; and, secondly, how having been able to traverse still air so readily one way, that matter failed to return as readily earthward under the attraction of gravity. Again the explanation, which at first seems a most probable one, that unusually high strata of moist air, with accompanying multitudes of ice particles, caused the phenomena alike of absorption and of reflection, seems negatived—first, by the entire absence of any other evidence of extraordinary meteorological conditions in September, October and November last; and, secondly, by the entire absence of any of the optical phenomena which necessarily accompany the transmission of sunlight through strata of air strewn with many ice particles.
We seem obliged then to adopt a theory, first advanced, I believe, by Mr. A. C. Ranyard, that the phenomena were caused by a cloud of meteoric dust encountered by the earth, and received into the upper regions of the air, thence to penetrate slowly (mayhap not till many months have passed) to the surface of the earth. Mr. Ranyard calls attention to the circumstance that probably the early snows of the winter 1883-’84 would bring down the advanced guard of such meteoric dust; and even as I write I learn that Mr. W. Mathieu Williams has followed the suggestion. He carefully collected the snow which fell in his garden, eighty yards from his chimneys and half a mile from any to windward. Slicing off a top film of the snow with a piece of glass he thawed it, and found a sediment of fine brownish-black powder. Ferrocyanide of potassium added to the snow-water produced no change of color, showing the absence of iron in solution, nor was there any visible reaction on the black dust till he added some hydrochloric acid. Then the blue compound indicating iron was abundantly formed all round the granules, and presently, as their solution was effected, a bluish-green deposit was formed, and the whole liquid deeply tinged with the same color. “It was not,” says Mr. Williams, “the true Prussian-blue reaction of iron alone, but just the color that would be produced by mixing small quantities of the cyanide of nickel (yellowish green) and the cyanide of cobalt (brownish white) with a preponderating amount of Prussian blue.”
If this explanation of the green sun and the extraordinary sunsets should be confirmed, it appears to me that a most interesting result will have been achieved. Of course, it is no new thing that as the earth rushes onward through space she encounters yearly many millions of meteoric bodies, large and small; nor ought it to be regarded as strange that beside these separate bodies, millions of millions in the form of fine cosmical dust should be encountered; but the actual evidence, derived from the behavior of sunlight (the red and yellow rays reflected and relative superabundance of green and blue rays therefore transmitted), would be an interesting and important addition to our knowledge of matters meteoric.—The Contemporary Review.
