Page:Popular Science Monthly Volume 30.djvu/441

Rh The products of some of the shops would almost deceive an expert; but the test of hardness is still infallible. The beautiful "French paste," from which imitation diamonds are made, is a kind of glass with a mixture of oxide of lead. The more of the latter, the brighter the stone, but also the softer, and this is a serious defect. The imitation stones are now so perfectly made, and are so satisfactory to those who are not very particular, that their influence begins to be felt in the market for real stones. By careful selection of the ingredients and skill and attention in manipulation, the luster, color, fire, and water of the choicest stones are, to the eyes of laymen, fully reproduced. There are a few delicacies of color that can not be perfectly given, for they depend on some undiscoverable peculiarities of molecular arrangement and not on chemical composition, but the persons who are to buy the stones know nothing of that. Yet Sidot, a French chemist, has nearly reproduced these peculiarities, including the dichroism of the sapphire, with a composition of which the base is phosphate of lime. Two other French chemists, Fremy and Fell, have produced rubies and sapphires having the same composition with the genuine stones, and nearly equal hardness.

The Future of Political Economy.—Mr.John Biddulph Martin, president, said, in the British Association's section of Economic Science and Statistics, that we need not despair of the future of political economy because its teaching, based too often on a priori reasoning, and too little on the experience of history, does not always square with the judgments of men. May we not claim that political economy has rather taken up wider ground, than that it has abandoned many of its outworks? It is no reproach to economic science to have done so; to have recognized as matters within its proper scope considerations that the older economists, concerning themselves with wealth in its narrow sense, as the summum bonum, and with the desire for its acquisition as the one mainspring of human action, would have regarded as sentimental and philanthropic. Humanity is many-sided, its units do not lend themselves to grouping or combination with the precision of mathematical symbols, and the experiments of the social philosopher are subject to disturbances unknown in the laboratory of the chemist. It is at this point that the statistical method comes in as an inseparable ally of economic speculation. The speaker proceeded to a fuller review of the merits and faults of the statistical method, and then dwelt at considerable length on the tendency of men to accumulate in cities.

Australian Paradoxes.—In connection with the recent determination of the oviparous character of the monotremes, "Nature" republishes the following list of the paradoxes of Australia from a work published in 1832: "But this is New Holland, where it is summer with us when it is winter in Europe, and vice versa; where the barometer rises before bad weather, and falls before good; where the north is the hot wind, and the south the cold; where the humblest house is fitted up with cedar; where the fields are fenced with mahogany, and myrtle-trees are burned for fire-wood; where the swans are black and the eagles white; where the kangaroo, an animal between the squirrel and the deer, has five claws on its fore-paws and three talons on its hind-legs, like a bird, and yet hops on its tail; where the mole lays eggs, and has a duck's bill; where there is a bird with a broom in its mouth instead of a tongue; where there is a fish, one half belonging to the genus Raja and the other half to that of Sgualus; where the pears are made of wood, with the stalk at the broader end; and where the cherry grows with the stone on the outside."

A New Incandescent Gas-light.—Mr.Conrad W.Cooke described, in the British Association, the Welsbach system of gas-lighting by incandescence. It consists in impregnating fabrics of cotton or other substances, made into the form of a cylindrical hood or mantle, with a compound liquid composed of solutions of zirconia and oxide of lanthanum (or with solutions of zirconia with oxides of lanthanum and yttrium). This mantle, under the influence of a gas-flame, is converted into a highly refractory material capable of withstanding the highest temperature that can be