Page:Popular Science Monthly Volume 31.djvu/879

Rh Virtues of Mountain Air.—It may be received as proved that mountain air is good in cases of consumption. Why it is so, may be explained by reference to the qualities of the air of great altitudes, among the most conspicuous of which are its purity, its rarefaction, and its coldness. All modern observers, says the "Lancet," are agreed that pure air is the most essential requisite in the treatment of the scourge. Pure air is not to be found near the great centers of human population, nor even in ordinary lowland country. To obtain it in perfection we must look to the ocean, the desert, or to great altitudes. In these three localities we are far removed from the ordinary sources of atmospheric contamination, and it is hardly necessary to seek to assign any precedence among them, as in each case the atmospheric purity is practically absolute. The next and most essential characteristic of the air, at great altitudes, is its rarefaction, by virtue of which it provokes deep and full respirations, thus promoting pulmonary expansion, and affording a favorable condition for the absorption of morbid deposits. It was long believed that rarefied air tended to promote hæmorrhage, and the well-authenticated stories of the sufferings of mountaineers from epistaxis and melæma, seemed to confirm the belief: But it was forgotten, when these stories were brought forward, that the conditions of blood-pressure at the various orifices are different from those which prevail in the internal organs. The congestion at the surface of the body must be accompanied by a proportionate anæmia of the deep-seated parts, and among them of the lungs. Hence, rarefaction of the air, so far from being injurious in cases of pulmonary hæmorrhage, affords a means for its arrest and relief. Cold is now known to be at least not unfavorable in phthisis. The air at great altitudes is not only very cold, but also very dry; and this combination of conditions tends to correct unhealthy secretions, while it is, at the same time, promotive of appetite and physical activity. This point is one of great magnitude.

Clothes-Moths.—Clothes-moths, injurious to woolen goods and furs, are of the species of Tinea—pellionella, biselliella, tapetzella, or rustica. The most common one is Tinea pellionella, which in its mature state carries about half an inch expanse of wings. Its fore-wings are shining, grayish-yellow, with three indistinct brownish spots in the middle, and its hind-wings are whitish-gray. It is abundant in houses, and may be found at any time between January and October, though most abundantly in the early summer months. The moth is innocent. The larva, which does all the damage, is a tiny caterpillar, dull whitish, with a reddish-brown head. It is the only one of the four species that makes a tunic or movable case for itself. This case is very ingeniously constructed, and consists of an outer layer of fragments of the articles it has fed upon, and an inner layer of silk, forming a soft and smooth lining. It is nearly cylindrical in form, but of slightly larger diameter across the middle, and a little flattened above, and it is open at both ends. These cases are varied in their appearance, and of different colors, according to the color of the goods from which they are formed. The case is enlarged as the insect grows, both by adding to its length and to its circumference. For the latter enlargement, the case is split and patched up in two slits at each end, with an ingenuity that borders on intelligence. The chrysalis state is assumed inside of the case, the caterpillar becoming, by throwing off its last larval skin, a little, yellowish-brown, helpless thing, similar in form to the chrysalides of the larger moths. The chrysalis is anchored by fine threads to the cloth in which the insect lives. From this the perfect insect emerges, when its time has been fulfilled, lays its eggs, and then dies. The eggs are extremely minute, and are deposited on the cloth, or in crevices and corners close to a supply of food. The young grubs begin life by attacking the old cases of their progenitors, with which they make cases for themselves, and begin to feed on cloths proper at a later period of life.

Polished Objects of Silicified Wood.—Mr. George F. Kunz, in exhibiting before the American Association polished specimens of jasperized and agatized woods from Arizona, referred to the description of these woods which he had published in the "Monthly" for March, 1886, their magnificent