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THE POPULAR SCIENCE MONTHLY. 



which are possible to a baby a few days old 

 is very small, aDd 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 satis- 

 faction, 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 wak- 

 ing 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 water- spider (Argyroneta aqua- 

 tica) 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 gradu- 

 ally 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 parad- 

 ing 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 consid- 

 eration 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 de- 

 ciduous-leaved trees, in which the vessels (ap- 

 pearing 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) even- 

 ly 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 pro- 

 nounced layer of autumn wood can be recog- 

 nized, which again changes to spring or sum- 

 mer 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 



