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Page:Popular Science Monthly Volume 18.djvu/875

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labor through a whole season with nothing more than this, he is liable to develop a subacute bronchitis, and occasionally a more dangerous affection. The morbific effects increase in the second and third years, and the shoveler will at last probably have to go to the hospital with a peculiar pulmonary disease, which may be of every grade and usually affects both lungs. The attack fixes him in the ward for at least three months, after which he may wholly recover if he goes into a new business, but, if he returns to his shoveling, he will soon fall a victim to lung-disease. A very few men continue to work in the elevators till they become old; and it appears that those who begin it at thirty-five or forty years of age bear it better than those who begin at twenty. Dr. Rochester considers a regulation and limitation of the hours of continuous labor, the sanitary regulation of lodging and boarding houses, and restriction in the use of ardent spirits, essential parts of any measures for checking this disease.


The Green Color of Oysters.—The fact that the green color of some oysters is caused by a variety of navicula, which is called Navicula ostrearia, is illustrated and established by experiments which have been recently made by M. Puységur, at Sissáble. A quantity of the green slime scraped from the edges of the "clears" was put, after the mud had been allowed to settle, into soup-plates. Perfectly white oysters, which had never been in the "clears," and the shells of which had previously been washed and brushed clean, were then put into the fluid. Other precisely similar oysters were put into plates of ordinary sea-water. In twenty-six hours after the beginning of the experiment, the oysters charged with diatoms had all acquired a marked greenish hue, while the other oysters remained unaltered. The experiment was repeated several times, with identical results; and the green color in the oysters was found to be more decided in proportion as the water was more highly charged with diatoms. The greenness disappeared on leaving the oyster for a few days in ordinary sea-water, to appear again when it was put in fresh water containing the navicula. It appears that the diatoms are drawn into the stomach of the oyster with the currents which it induces, and there part with their nutritive constituents. The chlorophyl is digested, and imparts its color to the blood, whence it happens that the most vesicular parts of the structure, as the bronchiæ, are most highly colored. The fact of the absorption of the diatoms was proved by the examination of the digestive tubes of the oysters experimented upon. Their stomachs, intestines, and exuviæ were strewed with carapaces of naviculæ.


Deep-Sea Explorations off the Coast of France.—A commission appointed by the Minister of Public Instruction in France has just accomplished an exploration of the depths of the Gulf of Gascony, and of a great submarine valley which lies parallel to the coast of Spain. The commission was composed of MM. Milne-Edwards, father and son, and several other naturalists, and Mr. Gwyn-Jeffreys and the Rev. Mr. Norman, of England. The expedition was completely successful, having collected at least five hundred species, nearly all of which are new to the fauna of the Gulf of Gascony, and some of which are new to science. Previous to this expedition, Messrs. Gwyn-Jeffreys and Norman had explored the fosse, or ditch, of Cape Breton, a curious submarine cavity in the sea-bottom of the department of the Landes, in which a connection was traced between the fauna of the Mediterranean Sea and of that part of the Gulf of Gascony.


M. Delaunay's Theory of Earthquakes.—M. J. Delaunay has proposed a theory that earthquakes, as well as many meteorological phenomena, are produced by the passage of the planets through the masses of meteors. The more severe seismic tempests, he believes, are caused by the passage of the larger planets through the cosmic groups, particularly through those in longitudes 135° and 265°, which appear to give rise to the August and November meteors. The passages of Venus, the Earth, and Mars through the groups seem to occasion only earthquakes of a secondary order; but each of these planets produces on its passage an increase of shocks in the months of August and November. The most violent and long-