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._