THE SUN,
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.