Page:Popular Science Monthly Volume 20.djvu/446

432 a Japanese student at Strasburg, has recently determined experimentally the specific resistance and the change of resistance to the galvanic current at all temperatures shown by all the kinds of hard carbon, including some artificial carbons and graphites. The highest specific resistance, at the freezing-point, was given by the graphitic compound used in Faber's lead-pencils, 952·0, and the lowest by Siberian graphite, 12·2, while the resistance of the artificial carbons prepared for electric lighting ranged from 36·86 to 55·15. The resistance in all the carbons decreased with a rise in temperature, the coefficient of decrease being greatest for Siberian graphite, the least for a carbon pencil prepared from coke. The thermo-electric force of all the samples was found to be plus to that of graphite.

states that the latest examinations of the chotts of Algeria and Tunis have shown that no serious difficulty need be apprehended in digging the projected canal which is intended to transform the marshy and unhealthy lowlands of the southern parts of those states into an interior sea. The ridge (seuil) of Gerbes is almost wholly formed of sands and siliceous or argillaceous marls, instead of being a mass of hard rocks, as some geologists have asserted.

is of the opinion that while it is easy enough to obtain a photographic image of the brighter parts of nebulæ, it must be extremely difficult to secure such complete images as will permit of their being used as an accurate standard with which to compare future observations. A nebula has no regular outline like the stars, but presents the appearance of flecks of cloud or haze, with indefinite borders and most diverse degrees of luminosity. The character of its photographic image will be modified by several circumstances, atmospheric conditions, instrumental power, sensibility of the plate, length of exposure, which can never be exactly repeated. Hence, two images of it will almost of necessity be different, though it may not have changed.

has made a study of the coloring-matter of the Medusæ and lias succeeded in extracting some of it. The matter was shown under a microscope having a power of twelve hundred, in the form of little irregular particles of a diameter of one thirty-thousandth of an inch included in the colorless protoplasm of the small cells. When extracted it proved to be soluble in acids, but insoluble in alkalies. The coloring particles appear as granulations in the neutral tissues of the living medusa, but arc dissolved and scattered after death as the tissues become acid.

technical school which was opened last fall, under the direction of the Metropolitan Museum of Art, had a very successful career during the winter, and was attended by one hundred and forty-three pupils. This fall, the art classes having been removed to new quarters, the building at First Avenue and Sixty-eighth Street will be occupied wholly by the trade-schools, which were to be opened on the 21st of November. It is the purpose of these schools to make thorough, efficient, and practical mechanics, who can earn a living by their trade. They will have departments of plumbing and sanitary engineering; house, sign, and decorative painting, with special courses in mixing colors, fresco-painting, and polishing in hard wood; and the science and practice of brick-laying. Practical instruction will be given by mechanics skilled in the different branches of their trades. The charges will cover the actual cost of instruction and of the materials used.

a paper on "The White Pine and the Lumber Industry of Michigan," Mr. W. H. Ballou shows that the quantity of pine timber in that State has decreased from 135,000,000,000 feet on 20,000,000 acres of land to 35,000,000,000 feet on 10,571,000 acres. Some 5,000,000,000 feet are now annually taken away, so that in seven years the supply will be exhausted. It almost seems a despairing task to hope ever to raise forests for another such enormous production, and science will have to devise other materials as a substitute for wood. Lumber is already made in boards an inch thick from wheat-straw, and can be colored so as accurately to resemble any real lumber. The inventor manufactures two thousand square feet of a more durable and cheaper material than lumber from a ton of straw.

birds, according to Mr. E. E. Fish, appear to possess powers of ventriloquism. A cuckoo, not a rod off, can make his voice appear to come from a furlong away; the thrush, singing from a low perch, seems to be in the tree-tops; the vesper-sparrow and field-sparrow on the road-side fence, as if singing from a distant field. The robin has a similar power of throwing its voice, and the cat-bird can sing in a loud, voluble sound or in a low, soft, sweet, and tender warble. The oven-bird, the smallest of the thrushes, singing from a distance, can throw its sharp, ringing notes in such a way as to cause the listener to believe that it is almost within reach.

F. R. S., first assistant at Greenwich Observatory, has been appointed Astronomer Royal to succeed Sir George Airy.