7i8 



THE POPULAR SCIENCE MONTHLY. 



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. f abre 

 has most frequently observed in these con- 

 ditions. 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 live- 

 ly 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 inflamma- 

 tion of the gums, together with muscular 

 pains in the limbs, and have often intestinal 

 troubles and spots of purpura. These phe- 

 nomena indicate the coming on of a mild 

 form of scurvy. The remedies are to be 

 found in whatever will improve the sani- 

 tary 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. II. 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 ex- 

 pressed 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 bot- 

 tom of the sea, and has risen from the wa- 

 ters, 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 con- 

 stantly diitinished, 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 Tnning-Forks. According 

 to observations recorded by Mr. C. V. Boys, 

 in " Nature," spiders are very sensibly af- 

 fected 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 trav- 

 eling. 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 per- 

 ceived 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 sound- 

 ing-fork was gradually brought near a spi- 

 der 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 Jour- 

 nal," 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 



