Of which so much has been said in these pages, continues to be
discussed with increasing interest by astronomers of both hemispheres,
who every day supply their quota of new ideas as the result of their
investigations. In THE CHAUTAUQUAN for March, 1884, the statement was
made that “it has already been demonstrated that the colored prominences
may be examined at any time when the sun can be seen; and it is believed
that Mr. Huggins has accomplished the difficult feat of photographing
the corona, so that it, too, may be scrutinized _at leisure_.” In the
April number of the _Nineteenth Century_, we find a very interesting
account by Mr. Huggins himself, of his operations in this line. As yet
the experiments have not been in all respects satisfactory; but so much
has been done as to leave no doubt of the final result. As Mr. H. tells
us, the great obstacle to overcome is the immense curtain of air, which
“hangs” between us and the sun, and absorbs some forty per cent. of the
sun’s light (and heat). This absorption renders our atmosphere as light
at least as the sun’s corona, and makes it as difficult of observation
as a lesser light placed behind a greater. The same atmosphere being as
bright, or brighter, than the stars, prevents our seeing the latter in
daylight. During an eclipse of the sun, the shadow of the moon affords
us a long, funnel shaped tube through this great air curtain (which may
be forty, or one hundred, or more miles in thickness) and we are enabled
through it to see the sun’s corona. But “on an average, once in two years
this curtain of light is lifted for from _three_ to _six_ minutes”—a very
contracted period in which to obtain a knowledge of a phenomenon that
we know is constantly changing. If we had a Joshua, who could command
sun, moon and earth to stand still for the space of a few hours even, we
might discover what we so much wish to know, what is this corona. Or, if
we could go beyond this atmosphere of ours—place it between us and the
earth, we might do without a Joshua. But we can not get outside. Then the
next best thing is to get as nearly outside as possible. Dr. Copeland
tried this by climbing an elevation of 12,400 feet. Prof. Langley
ascended Mt. Etna, and on Mt. Whitney ascended to the height of 15,000
feet; but at these heights the curtain was still too heavy, and no view
of the corona was obtained; or, as Prof. Langley expressed it, he “met
with entire non-success.” From reports in regard to observations made
in Egypt of the total eclipse of 1882, Mr. Huggins conceived the idea
of making a photographic plate so sensitive that it would distinguish
differences imperceptible to the eye, and on this plate take a picture
of the corona, and then examine it as one would the “photo” of a friend,
and mark its peculiarities. He made his first experiment in 1882, and
as a result “there seemed to be good ground to hope that the corona had
really been obtained upon the plates.” In 1883, a second attempt, under
more favorable circumstances was made, and “images of the sun exquisitely
defined, and free from all sensible trace of instrumental imperfection
were obtained.” On the 6th of May of the same year (1883) a total eclipse
of the sun occurred at Caroline Islands, and was there photographed by
Messrs. Lawrence and Woods, photographers of the Royal Society; and on
a comparison of these photographs of the sun’s corona during an eclipse
with his own taken both before and after the time of the eclipse (which
was not visible to Mr. H.), he had the satisfaction of seeing so strong
a resemblance as to convince him that he had photographed the corona
without an eclipse. Although having no doubt of the success of his
experiment, yet, on account of the unfavorable conditions of the climate,
it was determined to try a higher elevation; and the Riffel, near
Zarmatt, Switzerland, was selected as a suitable place to make further
trials. Mr. Ray Wood was selected as artist, and reached Riffel in July,
1884. But unfortunately, the “veil of finely divided matter of some
sort,” “of which we have heard so much in the accounts from all parts
of the earth of gorgeous sunsets and after-glows” seriously interfered
with the work; nevertheless, a number of plates were obtained on which
the corona showed itself with more or less distinctness. Not satisfied
with these results, Mr. Woods was deputed to go to the Cape of Good Hope,
where, under the direction of Dr. Gill, he is to make, or is, perhaps,
now making daily photographic representations of the corona, and laboring
fully to realize the anticipations of the esteemed Mr. Huggins.
Meantime our sun makes his accustomed rounds, bringing with him the usual
accompaniments, hot weather and the “dog days.” He will on the 1st rise
at 4:34 a. m. and set at 7:33 p. m.; on the 16th, rise at 4:43 a. m., set
at 7:28 p. m.; and on the 30th, rise at 4:56 a. m., and set at 7:17 p. m.
During the month the length of the day will decrease from 15 h. 1 m. on
the 1st to 14 h. 21 m. on the 30th. The declination will in the same time
decrease four degrees and forty-three minutes.