Page:Popular Science Monthly Volume 30.djvu/44

Rh in Switzerland, and since then at the Cape of Good Hope. So far nothing has been obtained, however, much in advance of Dr.Huggins's own first results. But since September, 1883, until very recently, the air, as every one knows, has been full of a fine haze, probably composed in the main of dust and vapor from Krakatoa, which has greatly interfered with all such operations. It is now fast clearing away, and, if Dr.Huggins's views are correct, it is reasonable to expect that a much greater measure of success will be reached next winter at the Cape, and perhaps during the present summer in England and Switzerland.

About the same time that Dr.Huggins was photographing in England, Professor Wright, of New Haven, was experimenting on the same subject in a different way. He reflected the sun's rays into a darkened room by a heliostat, cut out all but the blue and violet rays by a suitable absorbing-cell, and then formed an image of the sun and its surroundings upon a sensitive fluorescent screen, stopping out the sun's disk itself. He obtained on the screen, on more than one occasion, what he then believed and still believes to be a true image of the corona. But the aërial haze soon intervened to put an end to all such operations; for of course it is evident that success, whether by photography or by fluorescence, is possible only under conditions of unexceptionable atmospheric purity.

Both Professor Wright and Dr.Huggins base their hopes upon the belief, which seems to be warranted by the spectrum-photographs obtained during the Egyptian eclipse of May, 1882, that the light of the corona and of the upper regions of the sun's "atmosphere" is peculiarly rich in violet and ultra-violet rays—that the corona is far more brilliant to the photographic plate and to the fluorescent screen than to the eye.

Probably it must be admitted that at present the predominant opinion among astronomers and photographers is against the practicability of reaching the corona without an eclipse, by any such methods; at the same time, to the writer at least, the case appears by no means hopeless, and success is certainly most devoutly to be desired.

P.S.—The reports from the recent eclipse of August 29th, observed by British and American parties on the Island of Grenada, in the Southern West Indies, have just come to hand, and are strongly unfavorable to the reality of the coronal appearances obtained by Huggins and Wright in their attempts to render the corona visible without an eclipse.

Plates furnished by Mr.Huggins, and precisely similar to those which he has employed in his photographic experiments, were exposed by Captain Darwin during the totality (as well as before and after it), in an apparatus like Mr.Huggins's, with a time of exposure the same that he has been using, and were treated and developed according to his directions. The plates exposed during the totality show no corona