Page:Popular Science Monthly Volume 20.djvu/884

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THE POPULAR SCIENCE MONTHLY.

been buried with the vessel for about a thousand years, yet they retained their structure unimpaired, only they had become browned, or turned to brown-coal, and were easily identified as belonging to Hypnum squarrosum, Climacium dendroides, and other common species. No difficulty was met in making a satisfactory microscopical examination of them, and the cell-structure was brought out as plainly as if they had been freshly gathered. These, however, were only some of the more recent among several ancient specimens of peat-mosses that Dr. Müller reports that he has examined with similar results. The mosses of a tuft supposed to be from the lake-dwellings retained the individuality of their parts; and in a tuft taken from the turf under the drift in the Baltic provinces of Prussia, the plants, older by hundreds of thousands of years than the other specimens, were so well preserved that they were easily recognized by their form and cell-structure as belonging to a Scandinavian species of almost exclusively Arctic growth, which must have come down in the glacial period. We are often surprised at the good condition in which the unfossilized bones of prehistoric men and animals arc sometimes found; but the beautifully preserved condition in which these mosses occur is a far more wonderful phenomenon, because those organisms are among the plants of the slightest structure, and are not subject to fossilization. Still more wonderful is the perfection with which the minute structure of the diatoms is preserved.

 

Soldering by Pressure.—It is known that Faraday, in 1850, observed that two pieces of ice brought in contact and subjected to pressure would be soldered together, and unite into a homogeneous mass. This soldering, which took place the more readily in proportion as the pieces of ice wore nearer their melting-point, was regarded by Faraday as due to a special property of ice. Mr. W. Spring has recently undertaken a methodical series of experiments in the compression of a variety of bodies. That their condition of division might be well established, he reduced the substances experimented upon to powder, and subjected them in a mold of steel to a pressure of between two thousand and seven thousand atmospheres. Filings of lead were converted at two thousand atmospheres into a solid block, showing no granulation under the microscope, with a density slightly above that of ordinary lead. At five thousand atmospheres the lead became like a liquid, and ran into all the interstices of the apparatus. Powders of zinc and bismuth at five to six thousand atmospheres gave solid blocks, with a crystalline fracture. Approaching six thousand atmospheres, zinc and tin seemed to liquefy. Powder of prismatic sulphur was converted into a solid block of octahedric sulphur. Slack sulphur and octahedric sulphur passed into the same condition. Bed phosphorus passed into the denser state of black phosphorus. Thus, simple bodies undergo chemical transformations under the simple action of pressure. The transformation of amorphous powders, like that of zinc, into crystalline masses, is a kind of auto-combination. Some of the hard metals never lose their pulverulent structure under any pressure. Powders of the bioxide of manganese and the sulphurets of zinc and lead solder under pressure, and present the aspect of natural crystalline pyrolusite, blende, and galena; while silica and the oxides and sulphurets of arsenic do not suffer any agglomeration. Some pulverized salts are solidified by pressure, and become transparent. Hydrated salts—as, for example, sulphate of soda—may be completely liquefied at a high pressure. Certain organic substances—the fatty acids, moist cotton, and starch change their appearance, lose their texture, and undergo a very evident molecular packing.

 


NOTES.

The city of Charleston, South Carolina, according to the annual review of Mayor Courtenay, is paying a much higher relative rate for school purposes than Northern cities which have secured for themselves greater educational advantages. Compared with Boston, it gives, in proportion, nearly one half as much again for its primary public schools alone as that city for all its schools, and gives, besides, annual appropriations to the High School and Charleston College. The grievous burden has been thrown upon the city by the extraordinary needs of the colored population, and gives it, the city officers believe, a right to call upon the Government for help.