Page:Popular Science Monthly Volume 27.djvu/155

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143
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trical apparatus, where it would have to withstand a white heat. Mr. Dudley undertook the removal of the phosphorus, and found that this could be effected perfectly by heating the metal with lime in an electric furnace. The manufactured metal will then resist as much heat without fusion as the native metal. Iridium is sawed by a copper disk between four inches and eight inches in diameter, making twenty-five hundred revolutions a minute, and dipping into a bath of cotton-seed oil and corundum or diamond-dust. Many new uses are opening for it since it has been possible to melt and cast it. It is used for draw-plates, to replace the ruby plate, in the manufacture of gold and silver wire; for knife-edges for scales and balances; for tipping hypodermic needles; for the negative poles of arc-lamps; and for many other purposes. One of the most important applications is for the contact-points of telegraphic instruments. These points outlive many platinum contacts, and do not oxidize or stick. Mr. Dudley is making experiments, with a fair promise of reaching commercial success, in the electric deposition of iridium.


The Chaldean Lunar Cycle.—M. Oppert recently read a paper before the Academy of Inscriptions and Belles-Lettres on an Assyrian inscription concerning lunar cycles. More than twenty years ago he discovered in the inscriptions of King Sargon allusions to a great lunar cycle one of the revolutions of which terminated in the year b. c. 712. He was afterward convinced that this cycle was the period of 1805 years, after which the series of lunar eclipses recur in the same order. The knowledge of this period supposes continuous astronomical observations among the Chaldeans already of many centuries' duration. They began the calculation of the period from the year 11,542 before our era. This is also the year in which the Sothiac periods (of the Egyptians) of 1460 years begin, one of which ended b. c. 139. These two cycles of 1460 years and 1805 years play an important part in the chronological computations of the ancient East. Twelve of each of them form respectively 17,520 and 21,660 years, or 292 and 561 sixties of years, numbers which occur in the Bible, according, to M. Oppert, to express the length of time between the Flood and the birth of Abraham, and from the birth of Abraham to the end of the history in Genesis.




NOTES.

Thirty years ago pines were planted in the Sologne, a tract of waste land near Blois, France. Fifteen years afterward, as the pines were cut away, oaks sprang up spontaneously to take their places, thus tending to restore what history tells was the ancient vegetation of the country. M. Émile Hausen-Blangsted states, in illustration of the struggle for existence among trees, that the pine is dislodging the larch in the Grisons, while there and in the Jura the beech prevails over both. In Switzerland generally the beech gains the place of the oak, fir, and birch, and in Prussia the pine encroaches on the oak and the birch. Birches and the ash are extending themselves in the pine-forests of Russia, and the birch is dislodging the aboriginal pines in Siberia.

Mr. Frederick Ransome is making a cement from blast-furnace slag and lime, much superior to the cements previously made from this refuse matter. He uses lime from the gas-works, gets rid of the sulphur by calcination with coal or coke, and then dissipates it in the form of sulphureted hydrogen. While Portland cement breaks under a load of 818 pounds, this cement, under the same circumstances, exhibits a power of cohesion up to 1,170 pounds.

The Convallaria polygonatum, whose name indicates its relation to the lilies-of-the-valley, may fairly be described as a traveling plant. It has a root formed of knots, by which it annually advances about an inch from the place where the plant was first rooted. Every year another knot is added, and this drags the plant farther on; so that in twenty years' time the plant will have traveled about twenty inches from its original place.

The continued publication of the "Index Medicus" has been undertaken, after arrangement with the editors and the representatives of the late Mr. F. Leypoldt, the former publisher, by Mr. George S. Davis, of Detroit. The first number of the journal for the current year, having been necessarily delayed, will comprise the literature of January, February, and March. Further publication will be made monthly as usual. At the end of the year, in addition to the usual index of names, subscribers will be furnished with an index of subjects to the volume.