THE POPULAR SCIENCE MONTHLY.
and earth vibrations. A muddy stream issues from them, of varying fluidity, rolling along lumps of peat. Then the mud hardens and the bog sinks back, forming a funnel-shaped pool. The bogs studied by the author have been mostly on high ground, not in valleys. He believes that the eruptions are not caused either by excessive absorption of moisture or by gas explosions—the theories most readily suggested—but by land-slips, collapses, etc., of ground under the bog, which permit water or liquid mud to enter. This breaks up the bog mechanically, mixes with it and fluidifies it, and produces the outburst at the surface. The limestone formations in Ireland, with their large caverns and masses of water, are naturally subject to these collapses, which, with the vibrations they induce, are more frequent in wet years. The heavy rains preceding the bog eruptions are thus to be regarded as only an indirect cause of them. Herr Klinge supposes that similar eruptions occurred in past geological periods, the Carboniferous, for example, in some cases where fossil tree-stems are found in upright position.
In a paper in the British Association, on the Periodical Velocity of Bubbles in Vertical Tubes of Liquid, Mr. F. T. Tronton said that as a bubble ascended in a tube its changes of shape caused corresponding changes in its velocity, and consequently any given bubble if watched would be seen to have alternating maxima and minima of velocity. Further, the rush of water backward from the front to the rear of the bubble in the narrow channel between the latter and the wall of the tube was greatest when the bubble had its maximum elongation. By making the liquid more viscous we could arrive at a point where it became uncertain whether the bubble would ascend the tube in the long or flat condition, but having started either way it would continue in its original shape. At this particular viscosity the velocity of ascent was a maximum. Lord Kelvin, as Sir William Thomson is now called, suggested an application of this result to certain engineering problems, and particularly spoke of the possibility of nullifying the retarding effects of the viscosity of water upon the sailing of ships.
The Mexican jumping seed, or "devil's bean," is a euphorbiaceous plant of such poisonous properties that it is used by the Indians to envenom their arrow-points. It not having been scientifically identified to satisfaction, Dr. C. V. Riley has made a special study of it. The saltatory property is not intrinsic with it, but is imparted to it by an insect (Carpocapra saltitans), which secures lodgment within the bean and does the work. Dr. Riley believes that the insect is developed in the capsules of several species of the genus Sebastiana.
It is said that a larger cave than the Mammoth Cave, situated in the Ozark Mountains, near Galena, Mo., has been explored for a distance of more than thirty miles. In it have been found bones of recent and prehistoric animals, including the hyena and cave bear, and flint arrow-heads, but no bones of man. A few animals of the usual forms found in caves are still living there, including a white newt.
Phosphatic marls, according to the report of Mr. E. A. Smith, State Geologist, have been found in Alabama in the Cretaceous and Tertiary formations. When they were first brought to notice a spirit of speculation was aroused, which subsided when it was found that they did not include in commercial quantity high-grade phosphates suitable for exportation. Dr. Smith, however, regards this as to the advantage of the State, because it will cause the fertilizing material to be used at home, to the enlargement of its crops, as has occurred in New Jersey with its low-grade phosphates, instead of being exported as are the high-grade phosphates of South Carolina, which has, agriculturally, derived no more benefit than other States from its precious stores.
The eminent French philosopher and man of letters, Joseph Ernest Renan, died October 2d. He was the son of a sailor, and was born in Brittany, February 27, 1823. He was educated for the priesthood, and proved to be a remarkable student, but the result of his studies was to make him a theist instead of a Christian priest. His most widely known work is his Life of Jesus, which is one of a series of books on the origins of Christianity. He was also author of a History of the People of Israel, in five volumes, and wrote much on Oriental philology and archæology, in which subjects he was an adept. For many years he was Professor of Hebrew, Syriac, and Chaldaic in the Collége de France.
After some years of ill health, George Croom Robertson died September 20th, at the age of fifty-one. On account of illness he had recently resigned his professorship of Philosophy and Logic in University College, London, and gave up the editorial charge of Mind last year.