Popular Science Monthly/Volume 24/March 1884/Green Suns and Red Sunsets
THE whole world enjoyed, during the closing months of 1883 and through January, 1884, the spectacle of a succession of sunsets and sunrises marked by a brilliant, gorgeous red coloration. The phenomenon, if it had been only for a day or, two, might not have excited any particular remark, for in the United States the sight of a brilliantly-colored sunset is not at all unusual; but when it was found to be continuous for months, and to extend to every part of the earth, the impression became nearly universal that something uncommon was going on in our atmosphere or in space. The phenomenon apparently reached its culmination about the 27th of November, when the western sky was illuminated for more than an hour after sunset by a lurid glow, as of some great conflagration; and in many places the public thought it actually was the mark of a fire, while in some towns fire-alarms were sounded. The phenomenon first began to excite attention in the Eastern States at about the time of its brightest manifestation, in the last days of November. It was, however, remarked on the Pacific coast about a week earlier; in Europe early in the month; and at points in the Indian and Pacific Oceans as early as September. Among the earliest published mentions of it were those from the islands of Rodrigues, Mauritius, and Seychelles, August 28th, Brazil, August 30th, New Ireland, September 1st, the Gold Coast, Africa, September 1st and 2d, and one that was made in connection with the observation of a "blue sun" at Trinidad, September 2d, when, after dark, says the report, "we thought there was a fire in the town, from the bright redness of the heavens." At Ongole, India, after the sun had set, green, "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 that latitude within half an hour after the sun disappears. Captain Rolland, of the French Messageries steamer Saghelien, passing from near King George's Sound, Australia, to the Island of Réunion, observed, from the 25th of September to the 12th of October, a red light around the sun, which became more pronounced at sunset, and persisted for a length of time after that hour in proportion as the ship was in a higher latitude. "The colored part of the sky, which was at times extremely lively, had, about a half-hour before sunset, a very considerable surface, extending to a distance of forty-five degrees from the sun." The same coloring was seen in the morning. A correspondent writing from Wailuku, Sandwich Islands, to the "Hawaiian Gazette" of October 3d, speaks of the "most extraordinary" sunsets they had been having for some time past, "fiery red, spreading a lurid glare over all the heavens, and producing a most weird effect." The Attorney-General of West Australia wrote to Dr. J. W. Judd, October 27th, describing the same glow; and a letter from Umballah, India, October 30th, says: "There has been for some time a remarkable appearance in the sky every night. The sun goes down as usual and it gets nearly dark, and then a bright red and yellow and green and purple blaze comes in the sky and makes it lighter again. It is most uncanny, and makes one feel as if something out of the common was going to happen." The writer of this article has noticed from his own windows the interval of darkness between the setting of the sun and the appearance of the glow remarked in the letter.
The earliest observations of the glow in Europe appear to have been made about the 9th of November, after which time references to it and descriptions of it abound in the scientific and other journals. These descriptions agree with each other as to all essential features, and might be as well applied to the phenomenon as seen anywhere in the United States. The sky is generally spoken of as cloudless where the glow has appeared, although a few observers speak of light cirrus clouds floating in the air or passing over the sun or near it; and one observer at Ootacamund, India, mentions a green cloud that passed over the sun's disk, followed by a red one.
The red light is regarded by those who have paid most attention to the subject as associated with the blue or green sun which was observed in many parts of the East Indies early in September. It was noticed at Manila, in the Philippine Islands, on the 9th, when, during a "light dry mist," "the sun appeared colored green and diffusing over all the bodies it illuminated a strange and curious greenish hue, to the great terror of the islanders"; at Colombo, Ceylon, on the same day, when the sun, about forty minutes before setting, emerged from behind a cloud of a bright-green color. The whole disk was distinctly seen, and the light was so subdued that one could look steadily at it. The moon was also, to some extent, affected in the same way. A correspondent of the "Ceylon Observer," writing on September 12th from Puleadierakam, states that no light came from the sun, although it was visible, until nearly seven o'clock in the morning, and adds: "For the last four days, the sun rises in splendid green when visible—that is, about 10° from the horizon. As he advances he assumes a beautiful blue, resembling burning sulphur. When about 45° high, it is not possible to look at the sun with the naked eye; but, even when at the very zenith, the light is blue, varying from a pale blue early to a bright blue later on, almost similar to moonlight even at midday. Then, as he declines, the sun assumes the same changes, but vice versa. The heat is greatly modified, and there is nothing like the usual hot days of September. The moon, now visible in the afternoon, looks also tinged with blue after sunset, and as she declines, assumes a most fiery color at 30° from the zenith."
At Madras, India, Professor C. Michie Smith, of the Christian College, remarked the "perfectly rayless" and bright silvery-white color of the sun on the 9th of September. The same was noticed on the next day, but was succeeded, after the reappearance of the sun from behind a cloud, by a bright pea-green color. This peculiar color was again observed the next morning, and in the evening it "was a magnificent spectacle, and attracted the notice of every one. The silvery sheen was visible early in the afternoon, and the brightness of the sun rapidly faded, till by about five o'clock one could look at it directly without any difficulty. At this time there was a distinct tinge of green in the light when received on a sheet of white paper, while shadows were very prettily tinted with the complementary pink. As the sun sank toward the horizon the green became more and more strongly marked, and by 5.30 it appeared as a bright-green disk, with a sharp outline. In fact the definition was so good that a large spot (about 1' long) was a conspicuous object to the naked eye." The green suns were also seen for several days about the 22d. The spectrum, which Dr. Smith carefully examined, " showed clearly that aqueous vapor played a large part in the phenomena, for all the atmospheric lines usually ascribed to that substance were very strongly developed. But in addition to this there was a very marked general absorption in the red." Abnormal electrical conditions of the atmosphere were noticed at this place in connection with the phenomenon. Of an earlier date than any of these observations is a notice of a "green sun," remarked at Panama on the 2d and 3d of September, the same day on which a blue sun and lurid sky were observed at Trinidad.
The appearance of the green color in the sun and in parts of the sky outside of the sphere of the red glow was also remarked in numerous observations made in Europe. In one of the earliest notices of the spectacle published in England, the writer says that at sunset "a very peculiar greenish and white opalescent haze appeared about the point of the sun's departure, and shone as if with a light of its own, near the horizon. The upper part of this pearly mist soon assumed a pink color, while the lower part was white, green, and greenish-yellow." Another observer, at Worcester, describes the blue of the sky as having been changed to green and the green as being speedily replaced by the ruddy tint; and again, in the morning, "the color of the sun changed to an exquisite emerald hue, staining the landscape, and investing houses, buildings, glazed windows, and greenhouses with a remarkably weird aspect." At sunset of the same day, "the crescent of the moon, being just above the fringe of red light, assumed a lively green hue, and continued to exhibit the novelty of an emerald crescent" for a quarter of an hour. At other places, we read of the contrast of the glow with "the pale greenish hue of the clear sky around"; of a crimson arch stretching from southeast to northeast, "with a very clear greenish-blue sky beneath it in the east," and between the arch and the western horizon "a sky of a bright silver-white color, which was so brilliant that it gave us quite a second daylight"; at another, of the sky nearer the zenith appearing "of a sea-green tint." The sea-green tint in the east was observed at Rome; and at Berlin, according to Herr Robert von Helmholtz, there was "a greenish sunset at 3.50, an unusually bright-red sky with flashes of light starting from southwest. An interesting physiological phenomenon which recalls 'Contrast-Farben' was there beautifully illustrated by some clouds, no longer reached by direct sunlight; they looked intensely green on the red sky." The whole phenomenon was exhibited, according to Mr. J. Addington Symonds, with remarkable intensity at Davos-Platz in the High Alps; and on one occasion "the whole north-eastern region of the heavens was at the same time of the most vivid golden-green—the peculiar green of chrysoprase and some highly-tinted beryls. Each tone of light, rose and green, was reflected on the long, broad basin of valley snow, the blending of both colors being of a strange, bewildering brilliancy." The sun, at this place, appeared through the day "surrounded by a luminous, slightly opalescent haze—not at all resembling halo or iridescence of vapor."
The red glow and the green sun are most likely due to a common cause. The same medium which will give by transmitted light a green color to objects viewed through it, will, by the universal law of the absorption and reflection of light, reflect the red rays. The close connection of the two phenomena may be regarded as real.
The spectacle must be due to some peculiar condition of our atmosphere, for, if it was produced by any cause outside of the atmosphere, it would have been visible in some form through the night, whereas its duration corresponded tolerably closely with that of ordinary twilight; the cause must have been co-extensive with the atmosphere, for the glow lasted as long as the twilight, if not longer. The manifestation was not auroral or electrical, for no auroras have been seen which could reasonably be associated with it, and no electrical disturbances have been mentioned in connection with it, except at Madras. Professor Michie Smith, of Madras, and Professor C. Piazzi Smyth, believe that it is the result of peculiar conditions of vapor in the air; but, while this might easily account for colors lasting a few days, it is difficult to suppose a peculiar accumulation and distribution of ordinary vapors enduring for so long a period. Nevertheless, Mr. Lockyer has seen the sun green through the steam of a steamboat; it has been seen green through the mist of the Simplon; and Mr. Henry Bedford, describing the summer sunset and sunrise just within the Arctic Circle in July, 1878, in an English magazine of that year, said: "The color brightens, and some small streaks of clouds grow brighter and brighter, until the sun—the green sun—appears. A distant low range of rocks comes between us and its point of rising, and, as we glide on, an opening between them shows us the sun, a bright emerald, as pure and brilliant as ever gem that glistened; again we lose it, and again an opening shows it to us in its own golden light; and then once more it is the bright green; and now it rises higher, clears the ridge, and is once more the golden orb." The Rev. G. H. Hopkins, of Cornwall, England, has observed that in a clear sky, as the disk of the sun sinks down beneath the horizontal line of the ocean, the parting ray is of a deep emerald green. The effect is not produced if there are clouds around the sun. Dr. F. A. Forel, of Morges, Switzerland, mentions as a fact confirmatory of the opinion that meteorological factors alone can not furnish a sufficient explanation of the phenomenon, that in Switzerland the glow, after having decreased subsequently to the 3d of December, attained a second maximum on the 24th and 25th of the month, when the atmospheric conditions were quite different from those which prevailed in the country at the time of the first maximum.
The hypothesis that the spectacle was caused by the presence in the atmosphere of a cloud of "cosmic dust," which the earth has encountered in its travels, has been advanced by several observers, and is supported by Mr. Proctor. Mr. Nordenskiöld and other men eminent in science have taught us to believe that a meteoric dust falling upon the earth from space plays a much more important part in terrestrial economy than we have been accustomed to suppose; and they have collected, in uninhabited countries and far away from any volcano, quantities of dust—little rounded particles of metallic compounds unlike anything the earth is known to produce, and strikingly like what meteors of that size would be. Investigating whether an unusual quantity of such dust is now falling upon us, Mr. W. Mattieu Williams has found it in carefully selected snow from his garden. M. Émile Yung, of Geneva, has also found an extraordinary quantity of a similar dust in fresh snow that fell in the latter part of November and early in December on the steeple of the cathedral of Saint-Pierre, at "les Treize-Arbres," Mont Salève.Numerous suggestions have been made that the phenomena are the result of the diffusion through the whole atmosphere of the entire earth of ashes and cinders from the eruption of the volcano of Krakatoa, in the Straits of Sunda, which took place on the 26th of August last. This theory has the support of Professor Lockyer and other eminent men of science, and there is much to be said in favor of it. The principal objections to it are summarized in a remark by Mr. Proctor, "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 producing the after-glow 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." It will not do to limit our ideas of the effect that may have followed the eruption of Krakatoa by our knowledge of what has followed any other volcanic eruption; for the outburst at Krakatoa far exceeded in violence any event of the kind that is remembered in the history of man. Mr. W. J. Stillman, formerly United States consul in Crete, who has witnessed the explosions of two eruptions of the submarine volcano of Santorin, and has seen masses of rock weighing many tons thrown from a half a mile to a mile, and escaping gases expanding, after two seconds, into huge masses of cloud, at an elevation of from six to ten thousand feet, and then drifting away with the wind and dropping volcanic dust in its course, believes that on the enormously greater scale of the Krakatoa explosions the dust could have been thrown to the top of the atmosphere, there to drift over the whole earth; and he suggests that at such a height the distribution might be effected in twenty-four hours by a single revolution of the earth. Mr. Proctor's second difficulty is met by Messrs. Preece and William Crookes, who suggest that very finely divided particles of dust having an electrical charge of the same sign as that of the earth, may be kept suspended in the upper air for an indefinite period, by electrical repulsion; and Dr. Crookes adduces experiments showing how similar things have been done with electrified gold-leaf. Professor S. P. Langley contributes some interesting testimony on this point, which is based upon his observations on Mount Whitney, in 1881. On this mountain, from a height of twelve thousand feet, "we looked down," he says, " on what seemed a kind of level dust-ocean, invisible from below, but whose depth was six or seven thousand feet. . . . The color of the light reflected to us from this dust-ocean was clearly red, and it stretched as far as the eye could reach in every direction, although there was no special wind or local cause for it. It was evidently like the dust seen in mid-ocean from the Peak of Teneriffe—something present all the time, and a permanent ingredient in the earth's atmosphere. At our own great elevation the sky was of a remarkably deep violet, and it seemed at first as if no dust was present in this upper air, but in getting, just at noon, in the edge of the shadow of a range of cliffs which rose twelve hundred feet above us, the sky immediately took on a whitish hue. On scrutinizing this through the telescope, it was found to be due to myriads of the minutest dust-particles. . . . It is especially worth notice that, as far as such observations go, we have no doubt that the finer dust from the earth's surface is carried up to a surprising altitude. I speak here, not of the grosser dust-particles, but of those which are so fine as to be individually invisible, except under favorable circumstances, and which are so minute that they might be almost an unlimited time in settling to the ground, even if the atmosphere were to become perfectly quiet." Professor Langley thinks that the explosion of Krakatoa may have added millions of tons to the dust-envelope of the globe, and that the new contribution is not likely at once to fall to the surface again.
In illustration of this theory, we have the testimony of Captain Sir C. Fleming Stenhouse, who named the island, that after "Graham's Island" appeared in the Mediterranean in 1831, similar red sunsets to those the world has just been admiring were seen at Malta. A more striking record of a similar phenomenon is given in White's "Natural History of Selborne," Bonn's edition, page 300, where we read: "The summer of the year 1783 was an amazing and portentous one, and full of horrible phenomena; for besides the alarming meteors and tremendous thunder-storms that affrighted and distressed the different counties of this kingdom, the peculiar haze, or smoky fog, that prevailed for many weeks in this island, and in every part of Europe, and even beyond its limits, was a most extraordinary appearance, unlike anything known within the memory of man. By my journal I find that I had noticed this strange occurrence from June 23d to July 20th, inclusive, during which period the wind varied to every quarter, without making any alteration in the air. The sun, at noon, looked as black as a clouded moon, and shed a rust-colored ferruginous light on the ground and floors of rooms, but was particularly lurid and blood-colored at rising and setting. . . . The country people began to look with a superstitious awe at the red, lowering aspect of the sun; and, indeed, there was reason for the most enlightened person to be apprehensive, for all the while Calabria, and part of the Isle of Sicily, were torn and convulsed with earthquakes; and, about that juncture, a volcano sprang out of the sea on the coast of Norway." Cowper mentions the same phenomena in his "Task"; and Mrs. Somerville, in her "Physical Geography," traces their origin to the eruption of the volcano Skaptar, in Iceland, "which broke out May 8th, and continued to August, sending forth clouds of mingled dust and vapor, which spread over the whole of Northern Europe." It is stated in the "Annals of Philosophy," vol. ii, that the sun appeared of a blue color in England, in April, 1821; and it appears from other sources that a violent volcanic eruption had taken place in the Island of Bourbon in February of that year, and a destructive outbreak in Gunung Api in June of the previous year.
A curious counterpart to White's relation is given by Professor James Main Dixon of what he witnessed in Japan at the time of the eruption of Krakatoa. "During the two or three days at the end of August," he says, "we enjoyed fine, dry weather, but the sun was copper-colored and had no brightness. It was capital weather for traveling, but rather inexplicable. When we got to Nikko, the people came to us to inquire if some catastrophe were impending, for the appearance of the sun foreboded evil. We laughed at their fears, and assured them all was right. However, it seems that if the appearance of the sun foreboded no evil, it was a wonderful sign of the greatest earthquake and volcanic catastrophe on record. The fearful explosion of Krakatoa, in the Straits of Sunda, took place on August 26th; and there seems little reason to doubt that the monsoon had carried the volcanic dust along with it, the dust obscuring the sun. The distance is nearly three thousand miles."
Dr. Budde, of Constantinople, was assured, when traveling in Southern Algeria in 1880, that the sun has a decidedly blue color when seen through the fine dust of a Sahara wind. Mr. Edward Whymper, remarking upon a metallic-green coloration of the moon, observed on some evenings in December, says that the peculiar hue recalled to him a similar appearance which he had witnessed in South America when the atmosphere was charged with volcanic dust; and he has described the colorings seen by his party under a cloud of ashes from Cotopaxi in language which would almost precisely apply to the diversified appearances that are the immediate subject of our discussion. Extremely brilliant colorations of the sky have been mentioned by several travelers as common spectacles in a particular tropical belt. Colonel Stuart Wortley, who spent the year 1862 in Southern Italy, in the study, by the aid of photography, of the formation of clouds, was struck with the unusual colors of the sunsets during and after the eruptions of Vesuvius with which that year was distinguished. Four years ago, while sailing in the Pacific, he was much impressed with the fact that "very frequently the whole vault of heaven was overspread with magnificent and glorious coloring, and that in the higher regions of the air colors were found that were never seen in the horizon or below a certain height." Inasmuch as this exceptional magnificence and peculiarity of coloring only occurs in certain latitudes and in well-defined belts, he suggests that, seen in the new light that is now cast on the subject, "the constant stream of volcanic matter thrown out by the great volcanoes in the mountain-ranges of South America, and possibly from elsewhere, form an almost permanent stratum of floating matter, carried in certain directions and kept in certain positions by alternating currents in the higher regions of the air, and that to this stratum of volcanic matter much of the exceptional coloring, found to be associated with sunrises and sunsets in portions of the Southern Pacific Ocean, is due." As an interesting coincidence in connection with this view may be noticed the extraordinary fact, to which Mr. Lockyer has called attention, that "before even the lower currents had time to carry the volcanic products to a region so near as India, an upper current from the east had taken them in a straight line via the Seychelles, Cape Coast Castle, Trinidad, and Panama, to Honolulu, in fact very nearly back again to the Straits of Sunda."
Very strong evidence in favor of the theory of the agency of volcanic dust has been derived from the examination of the sediment in freshly fallen snow at Madrid, Spain, on the 7th of December, and of the mineral matter deposited by a rain that fell at Wageningen, Holland, on the 13th of December. The sediment at Madrid, besides the ordinary atmospheric dust of the city, contained particles of what appeared to be volcanic hypersthene, pyroxene, magnetic iron, and volcanic glass. At Wageningen, every drop of the rain that fell upon the windows left, when it dried up, a slight sediment of grayish-colored matter which was compared with original volcanic ash from Krakatoa that had been sent to the Agricultural Laboratory for analysis. Both the sediment and the volcanic ash were found to contain in common—1. Small, transparent, glassy particles; 2. Brownish, half-transparent, somewhat filamentous little staves; and, 3. Jet-black, sharp-edged, small grains resembling augite. These observations, say Messrs. Beyerinck and Van Dam, who made the analyses, "fortify us in our supposition that the ashes of Krakatoa have come down in Holland." On the 17th of November a fall of layers of gray and black dust took place at Storlvdal, Norway, and a fall of discolored rain near Worcester, England. Grayish sediments were found deposited on windows at Gainsborough and York, England, after a heavy rain on the 12th of December.
Mr. E. Douglas Archibald has suggested in "Nature" that, whether the cause of the phenomena be meteoric dust or volcanic ashes, the reflection arises from a definite stratum, and not merely from an atmosphere filled throughout with such dust. Professor Roujon, of Clermont, France, has also observed that two of the twilights, one following the other one day apart, "were so different in intensity as to provoke the supposition that the substance which produced them, at a great height, was not uniformly diffused, but moved in vast masses." This would serve to account for the variations that all must have observed in the brilliancy of the glow.
Mr. Edmund Clark has offered a suggestion upon which the theory that invokes the agency of aqueous vapor and the one which refers the manifestations to volcanic or meteoric dust may be combined, viz., that the dust may act as a nucleus for the condensation of any vapor that may exist at such a high level. The height of the mass of the matter producing the glow has been fixed by Miss Ley, of England, at thirteen miles.