Page:Popular Science Monthly Volume 10.djvu/131

Rh has hitherto been extracted, being silicates of nickel and magnesia, while the others are arsenio-sulphurets. They are found in serpentine rocks, which are very abundant in various parts of the island, associated with diorites, amphibolites, etc. Sometimes they appear on the various rocks as a beautiful green coating; sometimes they penetrate the rocks, giving them a more or less intense color; sometimes they form therein threads, which may assume the importance and regularity of veins; and sometimes, again, they occur in pockets. As might have been expected, the nickel is associated with iron, chrome, and cobalt, these metals, especially the two former, being very abundant; their stratification is analogous to that of nickel, except where cobalt is met with. The latter metal is associated with manganese, forming pure masses, of greater or less extent, in the midst of friable arenaceous rocks, composed of feldspathic and magnesian detritus.

Age of Trees in Relation to Time of Leafing.—In the course of a discussion, in the Paris Académie des Sciences, of the question whether the annual buds of a tree, as it grows old, preserve the characters of youth or share in the old age of the individual which produces them, it was stated that, according to observations made by Prof. Decaisne on the Robinia pseudacacia (common locust) of the Muséum d'Histoire Naturelle, the time of leafing does not vary with age. At Pisa, results a little different were obtained; there the gingko (Salisburia adiantifolia) and the walnut have been found to produce their leaves earlier in the season from year to year as they have advanced in age. On the contrary, the Æsculus hippocastanum, or horse-chestnut, is more tardy in proportion as it grows older. M. de Candolle, who was present at the meeting of the Academy, quoted observations carefully made every year since 1808 on two chestnut-trees at Geneva; these trees have leaved invariably between the ninety-third and the ninety-sixth day of the year. He further quoted the instance of a vine growing at Ostend. This vine has been observed during thirty-three years, and during the first eleven years it leaved on the one hundred and twenty-seventh day of the year; in the second period of eleven years, on the one hundred and twentieth; in the third, on the one hundred and sixth. Thus there would 'seem to be a continuous progression, the vine becoming more precocious in proportion to its advance in age.

Effects of Electricity on Particles suspended in Liquids.—Some interesting observations by Holtz on the effects of electricity on particles suspended in liquids are recorded in Poggendorff's Annalen. In giving an account of these observations, Holtz remarks that the "migration" of particles suspended in a liquid, subjected to electric currents, has long been known, and was thoroughly investigated by Quincke. But in all cases of such motion Holtz finds that there is, at the same time, a clinging of particles to one of the poles. This is sometimes so evident that one might construct an electroscope on this principle for ascertaining the polarity. Especially notable is the tendency of semen lycopodii in insulating liquids, particularly sulphuric ether, to cover the negative pole with a thick coating; while sulphur, cinnabar, or sulphide of antimony, in the same liquid, only coats the positive pole. A simple medicine-glass suffices for the experiment, a conductor or half-conductor being introduced through the stopper. The glass is held in the hand, and the conductor brought to an electric machine; the phenomenon then occurs. It is better, of course, to have the bottom perforated for insertion of the second pole, or to use an open glass, with the two poles pushed down into it. Either a frictional or an influence machine may be used.

Have Bees a Sense of Hearing?—Though the best observers deny to bees the possession of a sense of hearing, a writer in Newman's Entomologist relates an instance in which a hive of bees appear to have heard the summons of their queen. A swarm of bees had been gathered into a hive, which was allowed temporarily to rest upon a table. On lifting the hive, in order to set it upon the hive-board, the portion of the table on which the hive had stood was found to be covered with bees, which soon began to run about, from their having been