Page:Popular Science Monthly Volume 32.djvu/298

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286
THE POPULAR SCIENCE MONTHLY.

as the assimilative faculty of her pupils. In all object-lessons, various specimens of the object should be produced for examination and description; the little ones themselves must do the main part of the latter under the teacher's guidance, for these lessons are not only to enable the children to form new ideas, but they are also intended to train them in giving expression to such ideas. The teacher must make good use of the blackboard, and should practice drawing objects, so that she may illustrate with facility and precision any particular point of her lesson which can be so illustrated. All the materials, pictures, diagrams, etc., which the teacher provides from time to time should have their place in the school museum ready for future needs, and the children should be encouraged to bring contributions to such a museum, particularly such as the lessons they receive may suggest."

 

Artificial Production of Minerals.—According to M. Friedel, of the French Association, experimentation in the artificial production of minerals was suggested by the observation of the crystalline products accidentally formed in the metallurgic furnaces. Mitscherlich and Berthier took it up, and it has been advanced by a considerable number of experimenters. MM. Fouqué and Michel Lévy, by melting certain silicates and then exposing the vitreous mass to a lower temperature than that of fusion, have reproduced the identical minerals formed in the eruptive rocks, including the anorthite and labradorite feldspars, amphigene, pyroxene, peridote, and magnetic iron. While the granites have not been produced as such, their constituents—quartz and orthoclase and albite feldspars—^have been obtained in crystals. The first essays at reproducing the zeölite groups of minerals have been made by De Schulten, by heating the silicate of soda in tubes of aluminous glass. Spinel and corundum, among precious stones, were long ago produced by Gaudin, Ebelman, H. Sainte-Claire Deville, and Caron; and MM. Frémy and Feil have more recently prepared the ruby in large crystalline masses, which possess all the properties of the natural mineral except the susceptibility for cutting. A new advance seems to have been made in producing rubies, for artificial stones of fair dimensions have been met with in the trade, which, though not as bright and transparent as the natural gems, have their hardness, density, and optical properties. The diamond alone appears to have so far resisted all attempts at reproduction.

 

Somnambulism.—The phenomena of somnambulism and their connection with the nerve-centers have not been satisfactorily accounted for. They probably depend primarily, says the "Lancet," upon a directing impulse of sensory origin. Some of our actions often become by practice so nearly automatic that partial sleep or stupor does not arrest their unconscious performance. In somnambulism the intellect and the controlling will are torpid, while the sensori-motor man whom they should govern is awake and active. As in dreams the intelligent sensorium is alone drowsily active, with possibly a noticeable tendency to restless movement, so there may be other states of dreaming, in which the centers of motion are stimulated to a more powerful but unconscious action. Partial counteractives to somnambulism may be found in throwing off worries, and in the proper regulation of evening meals.

 

British Colonial Wines.—Among the features of the Indian and Colonial Exhibition held last year in London, was the department of colonial wines, in which the Australian wines played a prominent part. The soil, climate, and other Australian conditions differing from those to which European vines are subject, have stamped these wines with an individuality, in consequence of which they can never become exact substitutes for those of Europe. The lighter qualities of the Australian wines are believed, however, to be suited for consumption in England, where the commoner wines of France might be found too cold and thin for ordinary use. The phylloxera was discovered in Australian vineyards in 1877, but was checked in a very short time by the application of summary and effective measures. The Cape of Good Hope is capable of producing immense quantities of wine per acre, amounting in some vineyards to nine times the average in France, and four times in