THE STRANGE "SHINING NIGHT CLOUDS."
Since the summer of 1883, says the New York Herald, there has appeared a curious celestial phenomenon at night, known as the "shining night clouds." They have been visible in latitudes from 40 to 60 degrees, chiefly in June, July and early August, but later in the year in equatorial regions. Twice last December, they were reported from Pasta Arenas, South America.
One of the first appearances of the clouds was described by Mr. Robert Leslie, in Nature of 1883, as seen about ten P. M., near Southampton, England. A sea of luminous silvery white cloud lay above a belt or ordinary clear, twilight sky. The clouds were wave like and at a great elevation, extending all the way from west to north, and radiant with a light closely resembling that which shines from white phosphor paint. As witnessed in Bavaria, at a late hour on three nights in June and July 1885, the coloring of the clouds was pale steel blue, gradually changing through a dull green to yellow and orange below. They have generally presented colors of a light tone, but the intense pearly brilliance of irridescent clouds, and sometimes have an altitude as high as 30 degrees. Some persons have supposed that they are lighted by the sun. But, as observed last July 13, in England, they were invisible until eighteen minutes past ten P. M. when they became conspicuous and were at their brightest near midnight. It has been suggested that these sky wonders may be formed by the condensation of gases ejected from the Krakatos volcano in 1883. But this theory is not plausible. From their periodicity and their enormous altitude it seems very doubtful whether they belong at all to the earth's atmosphere.
Herr O. Jesse, of the Berlin Astronomical Observatory, referring to these facts in a recent circular appeals to mariners and all others to make observations on these clouds during the next three months. His request is made more urgent by the consideration that as the mysterious phenomenon was never noticed till 1883, it may soon disappear not to be seen again for centuries. Herr Jesse therefore requests that all who observe the shining clouds will record exact latitudes and longitudes of the place of observation, the exact time, the part of the sky in which the phenomenon is seen, form and color of the clouds, also sextant observation of the altitude of their highest points at precisely noted almost with spectroscopic tests of the light.
By photography the height of these clouds above the earth's surface has been made out as exceeding forty-five miles. From the fact it has been inferred that they may be of extraterrestrial origin, perhaps revealing the existence of a resisting medium in interplanetary space. If so, they would confirm the hypothesis of Encke, based on observations of the celebrated comet which bears his name, that there is a medium pervading space which offers resistance to a moving body, just as the air opposes the flight of a cannon ball. Eminent physicists have long reasoned that luminiferous aether pervades all space, and some have supposed it to be highly elastic, but absolutely solid. If the observations called for by Herr Jesse are accurately taken and prove that the height of the shining clouds exceeds the limits of our atmosphere, the result might be a very important addklee to the world's knowledge of cosmical agencies.
The luminous night clouds have only been seen in the twilight after the sun is about ten degrees below the horizon. They resemble cirrus or ice clouds. But the two can be distinguished, because cirrus in twilight are always darker than the surrounding sky, while the shining night clouds are always brighter than the surrounding key. As this summer may offer the last opportunity for observing the mysterious phenomenon it is to be hoped the Berlin astronomer's appeal will not be in vain.