Page:Popular Science Monthly Volume 29.djvu/589

Rh must be excluded. The real carpet-industry of the East is threatened with ruin from the competition of inferior English prison work and the introduction of modern so called improvements; and the modern Smyrna carpets have so degenerated "as even, in England, not to be accounted ornamental."

Life-History of American Snails.—Snails, according to Mr. Binney's monograph on "American Land-Shells," live in the forest, passing the greater part of their lives sheltered under the trunks of fallen trees, layers of decaying leaves, or stones, or in the soil. In the early days of spring they come out in companies, to sun themselves, and—possibly—to make love. Their eggs, which are laid when the weather has become favorable, are deposited in bunches of from thirty to fifty or more, slightly stuck together without any order, under the shelter of the leaves, or at the sides of logs and stones, generally at as great a depth beneath the surface as the animal can reach, and are then abandoned. This act is repeated two or three times during the season. The embryo can be seen within the egg in two or three days after it is laid, and emerges in the course of from twenty to thirty days, according to the weather. The young animal gnaws its way out of the egg, and makes its first meal out of the shell it has just left, and is then a snail of about a whorl and a half. But it grows very fast. It begins to prepare for hibernation at about the first frost, by ceasing to feed, becoming inactive, and fixing itself to the under surface of the substance by which it is sheltered, or burrowing a little way into the soil. The aperture of the shell looks upward, and the snail closes it by forming a glutinous shell-substance over it which is called the epiphragm. In this condition it reposes till spring. It also forms an epiphragm when it is in danger of being dried up in' long droughts. Snails dislike to expose themselves to the sun, and are most lively on damp and dark days and at night. The American species are for the most part solitary, and in this respect differ greatly from their European congeners, which are social. Those, however, which have been introduced from Europe—and they are not few—retain their native habits. The appendages which perform the office of teeth for snails are peculiar in structure and various in form, and they do good execution on whatever eatables the animals may attack. The slugs are snails without external shells; are more nocturnal in their habits than the other snails; and are seldom visible in the daytime, though there may be thousands of them around. They do not hibernate, although they are partially torpid in cold weather. They have the faculty of suspending themselves in the air by means of a thread which they spin from a mucus secreted within their bodies. They have also the power of secreting at any point, or over the whole surface of their bodies, a more viscid and tenacious mucus, having the consistence of milk and nearly the same color—which constitutes a fairly valid armor of defense for them. It protects them against irritating substances, against corrosive gases, water, alcohol, and heat. They leave a trace of their usual secretion on every object over which they pass. This secretion appears to be necessary to their existence, for death follows the failure of the power to form it. All the species are exceedingly voracious, and feed upon plants and dead animal matter. Living creatures are too quick for them. They do much damage in the night and then retire to their hiding-places, leaving the gardener to wonder in the morning what destroying monster has been working among his plants.

Autobiography of an Ancient Cyclone.—Mr. John T. Campbell, of Rockville, Indiana, has described in the "American Naturalist" his tracing, by means of "tree-graves," of the course of a cyclone which passed more than three hundred years ago. The date of the storm was marked by noting the age of an oak which had grown on the top of one of the "tree-graves" or mounds. Its course was found by inquiring where other "tree-graves" had existed or had been observed in the past, and was traced in a belt about a thousand feet wide for fifteen miles. The "tree-graves," as Mr. Campbell calls them, are the marks that indicate where trees have been blown over, and consist of a depression formed by the pulling up of