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Page:Popular Science Monthly Volume 56.djvu/410

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POPULAR SCIENCE MONTHLY.

with the Nubian buck. The latter animal is rather awkward in form and movement, but M. Crépin hopes to breed that out. Otherwise the Nubian is well acclimated, vigorous, and indifferent to cold, hornless, and a most excellent milker. Goat's milk generally is richer in caseine than cow's milk, and owes some of its special qualities to this fact, and to the further circumstance that the flecks of goat-milk cheese are smaller, softer, and more easily broken up—consequently more digestible—than those of cow's milk. Further, goat's milk is more nearly than any other common milk like in composition to human mother's milk; and it has the very great advantage that, the goat being less subject to attacks of tuberculosis and other dangerous disorders, it is comparatively free from the liability to convey infection. A single objection to the general use of goat's milk is the odor which is supposed to be characteristic of it, but M. Crépin affirms that this is not apparent when the goats are properly bred and kept. M. Crépin is experimenting with butter from goat's milk, and represents that he finds it very nice.

The fundamental principle involved in the new form of telemeter, or instrument for estimating the distance of visible objects without actual measurement, invented by Herr Zeiss, of Jena, is that of the stereoscopic effect which appears in natural vision, where the inclination of the eyes in concentrating on the object gives the sense of distance. The base line between the eyes is increased in the Zeiss instrument by means of a system of prisms so as to give a widened base of binocular vision, and of mirrors which give magnifying power. Double images are formed, the distance between which varies in proportion to the distance from the observer, and appliances are provided for measuring how far apart they are. The arrangement is fairly satisfactory for moderate distances—say of 3,000 metres, or about 10,000 feet.

M. Moissan believes that he has found a solution of the problem of the manufacture of ammonia from the a tmosphere, and consequently of rendering atmospheric nitrogen available in agriculture, by the artificial production of calcium nitride. While calcium undergoes no change in contact with nitrogen at the ordinary temperature, it is affected by it under the operation of heat, and finally burns in it, absorbing it rapidly and giving rise to a bronze-colored nitride. Thrown into water, this substance decomposes with effervescence, producing ammonia and calcium hydrate.

Prof. A. E. Dolbear, of Tufts College, Massachusetts, patented an invention for telegraphing without wires in 1886, which he claims covers all that Marconi is doing. He has sent messages with it for as long distances as five miles. According to his account he invented the system and made successful experiments with it as far back as 1882. He made an application for a patent, which was rejected by the Patent Office with the statement that it was contrary to science and would not work. "But as it did work, the claim was maintained in the office, and four years later, in 1886, a patent for it was issued." Professor Dolbear does not wish it to be understood that his patent is on the "art of wireless telegraphy," but that it covers everything that has been so far done in the art.

On the occasion of the visit of the French Association to the British Association, Prof. J. J. Thomson gave an exposition of the lines of research by which it has been concluded that the atom is not the smallest existing quantity of matter. Electro-chemical phenomena teach us to associate a definite amount of electricity with each atom of matter; but these recent researches indicate that under certain circumstances a much larger quantity of negative electricity may be conveyed by the atom, or else that the negative electrical charge resides on a small detachable portion of the "atom," which alone is concerned in the experiments. The positive charge seems to be distributed over the whole mass of the atom.

The merits of two methods of clarifying sewage—by dilution and by bacterial action—are discussed by Mr. Rudolph Hering in articles in the Engineering Magazine. Disposal by dilution in large streams of water is regarded as satisfactory in many places—where the water of the stream is not to be used