Page:Popular Science Monthly Volume 14.djvu/420

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406
THE POPULAR SCIENCE MONTHLY.

describes the instruments used for this research, and the manner in which they were employed. His conclusion is that, inasmuch as he failed to see in the corona spectrum the dark lines of the sun's spectrum, therefore the light of the corona is not all reflected light. The considerations which confirm him in this conclusion he states as follows: "Until this eclipse no observer has ever seen the dark lines in the spectrum of the corona except M. Janssen, who reported dark lines, notably D in 1871, but much more difficult to see than the bright lines. Several observers during the recent eclipse failed to see the dark lines, though they looked for them carefully. While I do not question the results of observers who report the presence of dark lines, I think all the observations taken together show that the continuous spectrum of the corona is not the spectrum of the sun. Aside from this, Prof. Arthur W. Wright made measurements of the polarization of the light of the corona, the first time, I think, it has been attempted, and has found the polarization to be but a small percentage of the whole light emitted. Although all reflected light does not reach us as polarized light, yet I think the small percentage of polarization, taken with the faintness of the dark lines, indicates that the corona is, to a considerable extent, self-luminous. The meteoric dust not only reflects the sun's light, but it is continually showering upon the sun, and in its passage through the atmosphere is rendered incandescent."

 

Investigating the Cotton-Worm.—Prof A. R. Grote is at present visiting the cotton growing States for the purpose of studying there the habits of the cotton-worm, and more particularly of determining whether the fly from which it comes is acclimated in those States, or whether it is annually imported. The latter opinion, as our readers are aware, is the one held by Prof. Grote, and it appears to be confirmed by this later investigation. According to his theory, the fly comes from the West Indies with the south winds every year. Having reached our cotton-producing States it there raises its first brood. The eggs are deposited on the under side of the cotton-plant leaf. In about three weeks the young worm "webs up" and becomes a black chrysalis in a thin cotton-cocoon within a fold of the leaf, and in due time the perfect insect emerges. This new fly, born in the South, moves in a general northerly direction, and in this way the country is overrun by the several ensuing broods. If the worm appears while yet the plant is young, the planter can exterminate it by the use of poison; but if it comes late it will not do harm enough to warrant much expense in killing it. Paris-green in a liquid form, or dilute carbolic acid, kills the worm when applied to the under side of the leaf as spray. Care must be taken to keep these poisons from the seed-cotton, and they should only be employed against the first brood of worms before the bolls open.

 

An Eastern Fish-Story.—A series of interesting letters is now appearing in Land and Water, entitled "Recollections of Bangkok," and in one of them a good description is given of the mode of capturing insect prey, followed by a species of "archer fishes," several specimens of which are kept in a small pond in the grounds attached to the palace of the "Second King" of Siam. It is much to be regretted that the author neither describes these fishes nor notes any particulars by which the species might be determined. Our readers will find in the Monthly for January, 1878, an illustrated paper on "Archer-Fishes." When the writer in Land and Water came to the pond its finny inhabitants were found to be in a high state of excitement, the cause of which was soon evident. "A small branch covered with black ants had been picked by one of the attendants off one of the overhanging trees; and, holding this a few feet over the pond, volleys of minute globules of water were directed at it from the mouths of all the little fishes crowded underneath. This was continued until all the ants were knocked off into the water. Then ensued a scramble for the prey. Any small insect within their range met the same fate, and they shot with the most unerring aim. As I stood watching the curious sight, close to the edge of the pond, a small fly lighted on my hand, but was hardly seated before a volley of watery bullets knocked him off his perch, though at a range of four or five feet.