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Page:Popular Science Monthly Volume 18.djvu/736

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enervation which compels frequent changes of the men in the gallery, sudoral or miliary eruptions, sometimes boils, rarely eczema, are among the phenomena which Dr. Fabre has most frequently observed in these conditions. If, while the gallery is constantly damp, the air is vitiated by poisonous or irrespirable gases, and if the water contains sulphates or sulphuric acid in solution, the men, in addition to pains in their limbs and difficulties in breathing, experience lively itchings and painful smarts wherever the surface of the skin has been abraded. Those who have labored for a long time in the damp galleries contract a chronic inflammation of the gums, together with muscular pains in the limbs, and have often intestinal troubles and spots of purpura. These phenomena indicate the coming on of a mild form of scurvy. The remedies are to be found in whatever will improve the sanitary conditions of the mines and the homes of the miners, and in the usual applications for scurvy whenever the symptoms of that disease appear.


Variability of the Level of the Ocean.—M. H. Trautschald, of Moscow, lately sent in a paper to the Geological Society of France, maintaining that the level of the ocean was not invariable, in which he expressed the following conclusions: 1. The level of the sea has fallen, as parts of the earth's crust have risen from the bottom above its surface; 2. The surface of nearly all the continents has once been at the bottom of the sea, and has risen from the waters, partly in consequence of upheavals, partly in consequence of the retreat of the ocean; 3. When the continents have been formed, a part of the waters of the seas is carried away from them, and held on the land as lakes, rivers, eternal snows, and as a constituent of organic matter—thus the quantity of water in the ocean has been constantly diminished, and its level has fallen; 4. As the earth cools, ice accumulates near the poles and on the mountains, water is soaked down more deeply into the crust of the earth, and mineral hydrates are formed everywhere. It follows that the level of the sea has been gradually falling ever since water has existed as a liquid upon the earth.


Spiders and Tuning-Forks.—According to observations recorded by Mr. C. V. Boys, in "Nature," spiders are very sensibly affected by the vibrations of a tuning-fork, and act toward it as they would toward a fly that comes to their web. When a fork, lightly touching a leaf, or other support to the web, was sounded, the spider, if at the center of the web, would lace the fork and feel with its fore-feet to find along which radial thread the vibration was traveling. Having become satisfied on this point, it would run along the proper thread till it reached the fork, or, if it came to the junction of two threads, would first stop and determine which was the right one. If the spider was not at the center of the web, and was not on a thread in contact with the fork, it had, when it perceived a vibration, to go to the center to see which radial thread was vibrating. It would then run out to the fork. If the fork was not removed when the spider had reached it, it would seize it, embrace it, and run along on the legs of the fork as often as it was made to sound, "never seeming to learn by experience that other things may buzz besides its natural food." If, when a spider had been enticed to the edge of the web, the fork was withdrawn, and then gradually brought near, the spider seemed aware of its presence and direction, and would reach out after it; but, if a sounding-fork was gradually brought near a spider that had not been disturbed, the spider would instantly drop; then, as soon as the fork was made to touch any part of the web, it would climb back and reach the fork with marvelous rapidity. By means of a tuning-fork a spider could be made to eat what it would otherwise avoid—even a fly dipped in paraffine—if its attention was kept fixed by the constant vibration of the fork.


Deterioration of Binding in Libraries.—Mr. H. A. Homes, in the "Library Journal," notices some causes additional to those arising from the use of gaslights, which may conduce to the deterioration of bindings in libraries. The modern methods of tanning do not give as durable a leather as the old processes, which it took months or years to complete. This may be the