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Page:Popular Science Monthly Volume 35.djvu/450

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THE POPULAR SCIENCE MONTHLY.

which are possible to a baby a few days old is very small, and a perception in the proper sense is beyond its capacity. "The being bathed or suckled does not cause it to smile, but its countenance expresses simple satisfaction, probably because of the absence for the time being of all uncomfortable feeling. Even sleeping infants a few days old lift the angles of the mouth in an incipient smile, if such it may be named. Very lively faces with dimples in the cheeks, but with closed eyes and other signs of sleep, are matters of common observation. On the twelfth day of life Preyer observed on the face of a waking infant most of the characteristics of a smile, though the mouth movements were imperfect. It was on the twenty-sixth day of life that he first observed all the signs of an intelligent smile in his own child."

 

The Nest of the Water-Spider.—The ways of the wafer-spider (Agyroneta aquatica) were described in M. Blanchard's article several months ago. A fuller account of the breeding habits of this arachnid is given by Mr. Joseph L. Newton in "Science Gossip." The author had placed several of the spiders in a tank, in which suitable plants were growing. All made themselves at home but one, which appeared restless. "For the first two days it quickly traversed from side to side, making repeated attempts to climb the glass to effect an escape, but eventually it settled down, and was soon busily webbing together in a diverging manner the pectinate leaves of the water crowfoot; then going within its leafy shade, . . . to weave its silken cocoon, or nest, in which, on the fifth day, 10th of June, through a small opening it had left unwebbed. . . could be observed the yellowish mass of eggs, surrounded with a glistening layer of air, distinctly separate from its still unfinished harbor. After a day or so of rest, it further extended the nest downward, in a bell or funnel form, until nearing two inches long; then closed the lower or wider portion, with the exception of two openings, one on each side, just to give leave of its exit or admission. This being completed, the mother could often be seen gracefully wending her way to the surface, and carrying down large successive bubbles of air, then carefully liberating them, one by one, in order to form a sufficient supply, in which it then remained for some days. From the end of the first week the eggs now gradually grew darker, and on July 1st, exactly the third week, the upper portion of the nest or cocoon was completely laden with young; when the large globule of air slowly began to diminish, and, on being exhausted, the mother seemed reluctant to find a further supply—as though she had done her duty. Here the young naturally became troubled, and in the fourth week were quickly parading the interior of the cell, apparently for escape, which they, through the course of nature, effected on July 11th; thus, in about thirty days, over forty young were actively playing their delightful and youthful part, each bearing its silvery bubble."

 

Annual Rings of Trees.—In regarding the annual ring as it is marked in different kinds and qualities of timber, Prof. Fernow says that there are to be taken into consideration the absolute width of the rings, the regularity in their width from year to year, and the proportion of spring wood to autumn wood. The spring wood is characterized by less substantial elements (vessels of thin walled cells in greater abundance), while the autumn wood is formed by thicker-walled cells, which therefore appear of darker color. In the wood of conifers and in that of deciduous-leaved trees, in which the vessels (appearing as pores on a transverse cut) are most frequent in the spring wood, the annual ring is usually very distinctly visible; while in those woods which, like the birch, linden, maple, etc., have the pores (or vessels) evenly distributed throughout the annual ring growth, the distinction is not so marked. Sometimes the gradual change in appearance of the annual ring from spring to autumn wood, which is due to the difference of its component elements, is interrupted in such a manner that seemingly a more or less pronounced layer of autumn wood can be recognized, which again changes to spring or summer wood, and then finishes with the regular autumn wood. This irregularity may occur even more than once in the same ring. Such double or counterfeit rings, which can be distinguished from the true annual ring by a practiced eye with the aid of a magnifying glass, have led to the notion that the annual rings are not a true indication of age. The