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 fa- cility 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 mu- seum ready for future needs, and the chil- dren should be encouraged to bring contri- butions to such a museum, particularly such as the lessons they receive may suggest."

Artificial Production of Minerals. — Ac- cording to M. Fricdcl, of the French Asso- ciation, experimentation in the artificial pro- duction of minerals was suggested by the observation of the crystalline products acci- dentally formed in the metallurgic furnaces. Mitscherlich and Berthier took it up, and it has been advanced by a considerable num- ber of experimenters. MM. Fouque and Michel L6vy, 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, py- roxene, peridote, and magnetic iron. While the granites have not been produced as such, their constituents — quartz and ortho- clase and albite feldspars — ^have been ob- tained in crystals. The first essays at re- producing the zeolite groups of minerals have been made by De Schulten, by heating the silicate of soda in tubes of aluminous glass. Spinel and corundum, among pre- cious stones, were long ago produced by Gaudin, Ebelman, H. Sainte-Claire Deville, and Caron ; and MM. Fremy 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 ad- vance seems to have been made in produc-

��ing rubies, for artificial stones of fair di- mensions 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 dia- mond alone appears to have so far resisted all attempts at reproduction.

Somnambnlism. — The phenomena of somnambulism and their connection with the nerve-centers have not been satisfac- torily accounted for. They probably de- pend 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 perform- ance. In somnambulism the intellect and the controlling will are torpid, while the sensori-motor man whom they should gov- ern is awake and active. As in dreams the intelligent sensorium is alone drowsily ac- tive, with possibly a noticeable tendency to restless movement, so there may be oth- er states of dreaming, in which the centers of motion are stimulated to a more power- ful but unconscious action. Partial coun- teractives 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 Exhi- bition held last year in London, was the de- partment of colonial wines, in which the Australian wines played a prominent part. The soil, climate, and other Australian con- ditions differing from those to which Euro- pean vines are subject, have stamped these wines with an individuality, in consequence of which they can never become exact sub- stitutes for those of Europe. The lighter qualities of the Australian wines are be- lieved, however, to be suited for consump- tion in England, where the commoner wines of France might be found too cold and thin for ordinary use. The phylloxera was dis- covered in Australian vineyards in 1877, but was checked in a very short time by the ap- plication of summary and effective measures. The Cape of Good Hope is capable of pro- ducing immense quantities of wine per acre, amounting in some vineyards to nine times the average in France, and four times in

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