Page:Popular Science Monthly Volume 51.djvu/583

Rh to use a field glass or small telescope, and, having once found the birds with it, to keep them in the field as long as possible. . . . Up and up they go, appearing smaller each moment till even the power of the glass is overcome, and the tiny specks vanish for the night. As you drop your arms wearily you find that the dusk has fallen, the bats are out, and the evening mists are rising; but the swifts must now be nearly on a level with those remote flecks of cloud which, at an immense height, are yet snowy in the sunshine."

The Light of Fireflies.—In experiments on the properties of the light of fireflies, Prof. H. Muraoka used plates of copper, aluminum, zinc, and brass of equal size, separated from the photographic plates on which they were severally laid by a layer of cardboard having a cross-shaped piece cut out of the center; wrapped the whole with three or four thicknesses of black paper, and exposed the bundle to the light of several hundred fireflies. His purpose was to learn whether the light from the insects after filtration through the black paper could penetrate the metals and affect the photographic plate, and to determine the relative transparency of the substances used. To his surprise, the parts of the photographic plate under the cardboard were most darkened, while those under the cross-shaped holes remained clear. The light of the insects seemed to behave very much like ordinary light, but, after "filtration," acquired properties similar to those of the Röntgen or the Becquerel fluorescent rays—properties apparently resulting from the filtration. Further, the filtered rays appeared to exert a peculiar action toward the cardboard—called by the author a suction phenomenon—similar to that of the lines of magnetic force upon iron. The properties of the filtered rays seemed to depend on the filtering substances, probably upon their thickness. They exhibited properties of reflection, but those of refraction, interference, and polarization were not observed, although the author believes that they exist. Their properties, generally, appear to be between those of the ultra-violet and the Röntgen rays. The insects used in the experiments had two or three rows of luminous spots on their under body; but the photographic plates were affected by the whole body as well as by the luminous spots, so that a complete image of the insect was formed when it was put upon the plate, the figure of the luminous part being, however, plainer than the rest.

Dust.—Micro-organisms are the great producers of disease, and dust is the chief carrier of micro-organisms. If there is any one ubiquitous thing, it is dust, and yet, notwithstanding its dangerous contents, it is being continually poked up, so to speak. As soon as the housemaid is up, it is hustled and dusted into the air, so that by the time the family is astir any germ which may have quietly settled in some corner where it could do no harm is floating about in the air, ready to appropriate any convenient and moist resting place, such as the human lungs or a bit of the breakfast, which will shortly carry it into one of the inmate's systems. The street-cleaning department, too, spends much of its energy in simply stirring up the dust about the streets; a little of it is carried off in carts each day, but every particle thus removed has probably been previously stirred up and allowed to settle a dozen times. The carpets and upholstery of modern houses were apparently designed as dust collectors. It is impossible to clean thoroughly a thickly upholstered sofa or chair, and almost as difficult to get a modern carpet or rug clean; these articles always contain more or less dirt, which in the case of the carpet is superficially stirred up at each sweeping. In fact, the reckless way in which house and street cleaning are handled is really appalling. Dusting should always be done with a damp cloth, and carpets cleaned by a closed sweeper well filled with wet tea leaves. The street-cleaning problem is simply a question of water supply. A thorough flushing of the streets once or twice in twenty-four hours offers a simple hygienic and thorough solution.

Pocket Gophers.—The pocket gophers, or Geomyidœ, according to G. Hart Merriam' s description, are North American animals exclusively, and most at home in the western United States and Mexico. Their whole organization is modified to suit a life underground. They are short-legged,