SCIENCE JOTTINGS.

Thames Star, Volume X, Issue 3089, 11 January 1879, Page 2

SCIENCE JOTTINGS.

The manufacture of artificial gems hat long attracted ibe attention of savant. The alchemists of the medioral ages laboured hard and long to discorer tome method of turning base metals into gold, but never thought of transmuting com* mon stones and minerals into precious stones. The woid strata is tho French for paste, and M. Strass is the inventorof a mixture which in his honor is called straps, with which, together with the metallic oxides, artificial diamonds and other .precious stones. are composed, equalling in point of beauty, and indistinguishable by ordinary tests from the real. This etrass is prepared in Tar/ing proportions (according to the gem to be imitated) from rock crystal, potash, oxide of lead, and occasionally a small quantity arsenic. The materials are melted in a hard porcelain or Hessian clay crucible* where they are exposed to a very strong heat for twenty-four hours, and then allowed to cool so slowly that a kind of annealing process toes on. Having made a strass which imitates the diamond, all the other gems may be easily produced by mixing the strass with such metallic oxides as will give the required colours. ' Most of the experimenters make a slight difference either in the materials employed, or in their proportion. Mr Douault produces imitation rubies by a particular treatment of the composition employed for topaz, which consists of a thousand parts of atrass, forty of a glass of antimony, and one of purple of cassias. This composition, at a particular stage of its preparation becomes an opaque mass* translucent at the edges, and affording thin luminss of a red color. The opaqje topaz matter is placed in a Hessian or net bio, rand loft '" «*■[-■'-' —'- fumcir— about 40 hours, when there is produced a beautiful yellow, which, when re-melted by means of a blow-pipe, will produce a strass nearly equal to the finest oriental rubies. The strass is finally handed over to the lapidary, who cuts or grinds it to the shaps of the real gem to be imitated* The perfect imitation of the real gem is the goal all the experimenters are striving to reach. The real object is to deceive the eye. The most perfect description of atrass, if it imitate no particular gem. has no real value. As the object of wearing precious stones is adornment, whatever answers that purpose at the least expense ought to give the best satisfaction.

The appearance in the heavens of a variable, or what we call temporary star, has recently occasioned a considerable amount of investigation and discussion among astronomers. This star was first noticed in November, 1876. Tbe first star of this kind erer catalogued was in the jear 334 be. During the Christian era they have appeared at irregular intervals, as in the years 386,945. 1264.1572. 1604, 1670. 1844. 1866, and 1876. This latter star made its appearance in tbe constellation Cygnus, not only where there was no visible star, but where in tbe most complete star maps none was marked. Tbe star that was seen on the 12th of May, 1866, at a star of the tenth magnitude, in the course of two days became a star of the second magnitude, and then sank through one telescopic magnitude after another until it again shone as % teoth magnitude star. As the 18(16 star faded from riew, the spectrosoopid lines. ! indicative of glowing hydrogen died out, and only the ordinary stellar spectrum remained. In the star now - Attracting attention, the spectroscopio lines at the first we c such as left no doubt of its being a sun; yet such have been the changes through which it has passed, that on the 3rd of September of the present year Lord Lindsay announced, " There is little doubt but that this star has changed into a planetary nebulas." Other eminent astronomers, among whom we may mention Mr Proctor, argue that it has passed into a condition of gaseous nebulosity. Well may such events astonish the most thoughtful and observant. What is the fuel which feeds such quick and awful fires P What if a similar catastrophe should befal our own sun P Enor* mous quantities of hydrogen must be liberated to cause a star to flare up from six to eight hundred-fold in two days* Professor Lewis Swift, in a recent letter,, asks,"May not the same fate befal our sun? Increase its light and heat but twofold, and every creature on the earth would die; increase it eight hundred fold, like the star of 1866, and a fulfilment of Peter's prophecy would be realised—' the elements shall melt with fervent heat'"