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THE POPULAR SCIENCE MONTHLY. 



Dr. Hanichi Muraoka, a Japanese stu- 

 dent at Strasburg, has recently determined 

 experimentally the specific resistance and 

 the change of resistance to the galvanic cur- 

 rent at all temperatures shown by all the 

 kinds of hard carbon, including some ar- 

 tificial carbons and graphites. The high- 

 est specific resistance, at the freezing-point, 

 was given by the graphitic compound used 

 in Faber's lead-pencils, 952 - 0, and the low- 

 est 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 Si- 

 berian graphite, the least for a carbon pen- 

 cil prepared from coke. The thermo-electric 

 force of all the samples was found to be 

 plus to that of graphite. 



M. de Lesseps states that the latest ex- 

 aminations of the chotts of Algeria and Tu- 

 nis have shown that no serious difficulty 

 need be apprehended in digging the pro- 

 jected canal which is intended to transform 

 the marshy and unhealthy lowlands of the 

 southern parts of those states into an inte- 

 rior sea. The ridge (seuil) of Gerbes is al- 

 most wholly formed of sands and siliceous 

 or argillaceous marls, instead of being a 

 mass of hard rocks, as some geologists have 

 asserted. 



M. Janssen is of the opinion that while 

 it is easy enough to obtain a photographic 

 image of the brighter parts of nebulae, it 

 must be extremely difficult to secure such 

 complete images as will permit of their be- 

 ing 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 charac- 

 ter of its photographic image will be modi- 

 fied 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 dif- 

 ferent, though it may not have changed. 



Mr. Mackendrick has made a study of 

 the coloring-matter of the Medusa; 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 diame- 

 ter of one thirty-thousandth of an inch in- 

 cluded 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 granula- 

 tions in the neutral tissues of the living 

 medusa, but arc dissolved and scattered 

 after death as the tissues become acid. 



The technical school which was opened 

 last fall, under the direction of the Metro- 

 politan Museum of Art, had a very success- 

 ful career during the winter, and was at- 

 tended by one hundred and forty-three pu- 

 pils. 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 No- 

 vember. 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 plumb- 

 ing and sanitary engineering ; house, sign, 

 and decorative painting, with special courses 

 in mixing colors, fresco-painting, and polish- 

 ing in hard wood ; and the science and 

 practice of brick-laying. Practical instruc- 

 tion will be given by mechanics skilled in 

 the different branches of their trades. The 

 charges will cover the actual cost of instruc- 

 tion and of the materials used. 



In 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 lum- 

 ber. The inventor manufactures two thou- 

 sand square feet of a more durable and 

 cheaper material than lumber from a ton 

 of straw. 



Many birds, according to Mr. E. E. 

 Fish, appear to possess powers of ventrilo- 

 quism. 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. 



Mr. W. H. M. Christie, F. R. S., first as- 

 sistant at Greenwich Observatory, has been 

 appointed Astronomer Royal to succeed Sir 

 George Airy. 



