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Page:Popular Science Monthly Volume 18.djvu/294

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The Markings of Meteoric Stones.—M. Daubrée, the eminent French geologist, in his recently published work on "Synthetic Studies in Experimental Geology," describes some experiments that he has made for the purpose of ascertaining the cause of the peculiar appearance of the surface of meteoric stones. These bodies are covered with a blackish coating, which is sometimes dull and sometimes brilliant, and indicates unmistakably that they have suffered modifications in passing through the atmosphere. Their fracture presents a globular surface, similar to the structure of terrestrial rocks, showing that a strong cohesion has been produced at the moment of their formation. The outer surface is also covered with rounded depressions forming little capsules. M. Daubrée had remarked that when a cannon loaded with coarse-grained powder was fired off, some grains, which were only partly burned, would fall at the muzzle of the piece. The hollowed surface of these grains bore a striking resemblance to the forms seen on the meteorites. He then performed an experiment by taking a rectangular plate of steel, rolling it up in such a way that it should be fully enveloped by the gases from the powder, putting it in a closed steel chamber, with a quantity of powder, and firing off the powder by means of the electric spark. The duration of the deflagration was less than half a second. The gases acquired a tension of from one to two thousand atmospheres, and a temperature estimated at about 3,600°. The action, though of very short duration, gave surprising results. The surface of the plate was hollowed into irregular furrows, which demonstrated the force of the gaseous currents, and a powder of sulphuret of iron was found in the bottom of the vessel. A half a second, then, was all the time that was required to produce a partial fusion of the steel, a considerable blowing up by the gases, and such a chemical action as the formation of a sulphuret of iron. The experiment was repeated with dynamite and other explosives, with identical results. From them, M. Daubrée has deduced the following interpretation of the meteoric phenomena: the meteorites enter the terrestrial atmosphere with an enormous swiftness. The great pressure of air to which they are subjected explains the incandescence which takes place, and the superficial fusion of the mass. The part of a projectile of this kind which is at the moment in front rams the air and compresses it exceedingly, and causes it to be agitated by energetic gyratory movements. In whirling thus, under such pressure, the air tends to screw and hollow out whatever it rubs against, and this mechanical action is accompanied and reënforced by a chemical action due to the combustible nature of the meteoric rocks at these high temperatures. These rocks contain enough particles of iron in the native state, or as a sulphuret, to largely favor combustion and disaggregation. Under these circumstances, the hollows are produced, which appear on one side or on all sides of the projectile, accordingly as it has not or has a motion of rotation. M. Daubrée has given to these hollows the name of piezoglyptes.


Relation of Age and Marriage to Suicide.—It has been a mooted question whether the old or the young were more prone to suicide. Statistics published by Dr. Bertillon, in an article on marriage in the French "Encyclopædic Dictionary of the Medical Sciences," prove that the propensity increases with advancing age. They are reënforced by statistics recently published in Sweden, which lead to substantially the same conclusion. The proportion of the number of suicides of the more advanced ages to the whole number of persons of corresponding ages appears to be less in Sweden than in France, but aside from this the proportion increases regularly in both countries from the age of fifteen or twenty years to that of sixty years. After about sixty years the tendency in both countries appears to diminish. The proportion of suicides among women is less at all ages than among men, but increases with the advance of years as with the men. The statistical work of Signor Morrelli, recently published at Milan, lends additional support to these views. Dr. Bertillon has also collected facts bearing on the effect of marriage upon the tendency to suicide, from which he has deduced the principles: 1. That widowers and widows commit suicide more frequently than married persons; and, 2, that the presence of children in the family makes the probability of suicide more re-