Page:Popular Science Monthly Volume 27.djvu/447

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sessing a power of absorption more intense and lying nearer to the yellow of the spectrum, and obtained in eosine and in various derivatives coloring substances which hardly possess more than a broad absorption band in the yellow, and with which he obtained the desired result. When these bodies were mixed in due proportions with the dry gelatine plates, the yellow of the colored objects appeared quite clear on the photograph, but the blue was still always brighter. Professor Vogel then inserted a yellow glass between the object and the camera, which partly absorbed the blue rays, leaving the yellow unimpaired, and obtained photographs in which the blue, as well as the green and yellow, and partly even the red, parts of the colored objects presented to the observer's eye the same vivid effects as the original.

The Objects of Bathing.—The object of bathing, says a writer in the "Saturday Review," is fourfold: to produce a certain amount of nervous shock, that should be followed by reaction and an increased circulation of the blood on the surface, resulting in a more rapid change of tissues; to lower the temperature of the body; to cleanse the skin; and to produce pleasurable feelings, and, in connection with swimming, the beneficial effects of one of the best forms of physical exercise. The nervous shock and the reaction from it, following the first contact with the water, are important points, and to obtain them the plunge or the douche is preferable to any other form of bath. To wade up to the middle and stand shivering and fearful of the momentary feeling of discomfort is neither healthy nor pleasant, and timid persons who dare not plunge boldly into the water should be content with the douche-bath. A large garden hose, with a high pressure of water, held at a distance of fifteen or twenty feet from the body, will give an idea of this most delightful curative and bracing agent. Sea-bathing differs from out-door fresh-water bathing in the greater specific gravity of sea-water and its consequent greater buoyancy and more uniform temperature, while the pure air, sunshine, and better sanitary surroundings of sea-side places contribute largely to the results. Mineral baths, as such, have no particular superiority over other baths of the same density and temperature. In addition to the greater healthiness and enjoyableness of out-door bathing, it is probable that the simple exposure of the body to the sun and fresh air is of real benefit, and contributes to the sum total of the good results. Cramps are considered one of the great dangers of bathing, but when they are fatal it is probably the result of syncope or fainting, from failure of the heart's action. A good swimmer in vigorous health would hardly be wholly disabled by a cramp of only a part of his limbs.

Structure of the Edible Birds' Nests.—Mr. Pryer, whose account of his visit to the Gomantin Caves, in North Borneo, has furnished a fund of information respecting the edible birds' nests of the Chinese, has published in a Japan paper an article correcting some misapprehensions that he has found to exist on the subject. That the nests are made from the saliva of the bird he regards as a physical impossibility, for a bird could not secrete in a few days a mass of saliva more than equal, when dried, to the entire bulk of its own body, and then do this nine consecutive times a year. He thinks that some saliva is used by the birds, the alga? being worked up in the bird's mouth in the same manner that mud is worked up by the Japanese swallow. Mr. Pryer at first thought that the black nests owed their color to their being made of the brown outsides of the algae, while the white nests are made of the inside. This is not correct, for the birds can use only the inside; the black nests are simply white nests grown old and frequently repaired.

How to sleep well.—In sleeping, much depends on securing a comfortable position. Lying on the back would seem to give the most ease, but general experience and practice prove that it does not, and it is liable to some definite objections. In a weakly state of the heart and blood-vessels, and in certain morbid conditions of the brain, the blood seems to gravitate to the back of the head, and to produce troublesome dreams. Persons who have contracted chests, and who have had pleurisy and retain adhesions