Page:Popular Science Monthly Volume 25.djvu/735

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an engineer, Alessandro Giordano, called attention to the danger of extending these excavations farther toward the city. Add to this the action of the carbonic waters of the thermal springs in hollowing out caverns in the trachytic rocks, and we have probable a condition of the subsoil and underlying formations extremely perilous to the stability of the foundations of the town, and one under which Just such a disaster as has overtaken it might be readily conceivable.

M. Wroblewski has been investigating the boiling-points of air, oxygen, nitrogen, and carbonic oxide, at the ordinary pressure of the atmosphere, and fixes them as follows: Oxygen, 299° Fahr.; atmospheric air, 314°; nitrogen, 315·5°; carbonic oxide, 314∙4°. Atmospheric air seems destined to be the refrigerant of the future, for it is already at hand, and will produce a degree of cold that is only insignificantly exceeded by that induced by any other substance. It must, of course, be first compressed and liquefied; then, when it is to be used, it will be let loose to freeze by its evaporation, as is now done with other refrigerants operating in a similar way.

M. Gustave Hermite describes a method of taking phosphorescent photographs, which he has found to be practicable with any phosphorescent substance, but for which he prefers sulphuret of calcium, a material from which a luminous paint is made. This substance is very sensitive to light, and assumes a phosphorescence the intensity of which is proportioned to the intensity of the light to which it is exposed, rather than to the length of the exposure. A glass plate is painted with it, and is exposed in a bright light in the face of the object of which a picture is desired. The picture appears very distinct when the plate is taken into the dark. It may be revived afterward by breathing upon the plate, and then passing a hot flat-iron over it. Sulphuret of calcium becomes phosphorescent under the influence of heat (300° C.) as well as of light.

M. E. L. Trouvelot has concluded, from observations on the planet Saturn for several years, that his rings are not fixed but very variable; and that the hypothesis that they are composed of multitudes of corpuscles or minute satellites, revolving in independent orbits, is very probable, and affords the best explanation of the phenomena.

 


NOTES.

Dr. Austin Flint is quoted in the seventeenth report of the Peabody Museum as authority for the statement that the metates or grinding-stones, used in Nicaragua, are obtained from the old burial-mounds. Dr. Flint informs us that this is true, so far as the northwestern departments of Costa Rica are concerned, but that the idea of the same being the case in Nicaragua is an error, arising from an inaccuracy of his own expression incidentally committed in writing hurriedly on another subject. The metates in universal use in Nicaragua are made there now, and are much inferior to those found in the mounds; and, being of much less value, they are gradually being bought in Costa Rica.

The biological class at the University of Cambridge has outgrown the capacity of any lecture-room to accommodate it, and at the last term numbered two hundred in the elementary department alone. A considerable number of graduates remain at the university engaged in biological research, and the museums are continually being enriched with specimens presented by recent graduates who are traveling on scientific expeditions.

General Sir Edward Sabine, for ten years President of the Royal Society, and for twenty years General Secretary of the British Association, recently died at Richmond, England, aged ninety-four years. After serving on the English side in the war which we call the War of 1812, he became officially engaged in scientific work, and served his government and the scientific associations for twenty years in astronomical and magnetic investigations, in the course of which he was connected with several Arctic and marine expeditions. He was elected General Secretary of the British Association in 1839, Foreign Secretary of the Royal Society in 1846, and Vice-President and Treasurer of the same in 1850; and was President of the Royal Society from 1861 to 1871. Our present conception of the exact figure of the earth is said to be mainly due to his investigations. A portrait and sketch of General Sabine were published in the second number of Vol. II of "The Popular Science Monthly."

M. Pasteur, in consideration of his researches in hydrophobia, has been awarded a gold medal by the French Société Centrale pour l'Amélioration des Races des Chiens.