Page:Popular Science Monthly Volume 7.djvu/396

382 drawings are made with water-colors, the body of which is white-lead. Those portions of the surface which are not painted are covered with varnish. The article is then placed in dilute nitric acid, whereby the paint is dissolved, and the surface of the metal is etched to a certain depth. The article is then washed with water, and immediately placed in a silver or gold bath, and a layer of the precious metal deposited by electricity on the exposed portions. When the latter operation is finished, the varnish is removed, and the whole surface ground or polished, so that the ornamented portion is just even with the rest of the surface. A specially fine effect is obtained by producing a black bronze of sulphuret of copper on portions of the surface between the silver ornaments. A copper vase then has three colors, black and white drawings on a red-brown ground of suboxide of copper.

Ancestors of the Esquimaux.—Charles E. DeRance, in one of his papers on "Arctic Geology," points out some of the many striking resemblances between the modern Esquimaux and the paleolithic man of Southern France. These two peoples, separated so widely in time and space, were alike in their artistic feelings and methods of incising, on tusks, antlers, and bones, representations of familiar objects; alike also in their habit of splitting bones for marrow, and accumulating them around their dwellings; in their disregard for the sepulchre of their dead; in their preparation of skins for clothing, and in the pattern of the needles used in sewing them together; alike also in their feeding on the musk-sheep and the reindeer, and in countless other characteristics. It is wellnigh impossible to resist Prof. Dawkins's conclusion that the Esquimaux is the descendant of paleolithic man, who retreated northward with the arctic fauna with which he lived in Europe.

Antidote to Atropia.—Dr. G. Rückert has made the interesting discovery that the poisonous alkaloid muscarin (extracted by alcohol from the mushroom Amanila mitscaria) is a perfect antidote to atropia, and vice versa. The pupil of the eye, enlarged by atropia, is contracted by muscarin. So, too, the depression of temperature induced by subcutaneous injection of muscarin is counteracted by the other alkaloid similarly injected. The heart of a frog, whose action had ceased from thirty to sixty minutes under the influence of muscarin, had its activity restored by the exhibition of atropia. The relation of quinine to the specific poison of intermittent fevers is probably analogous to that between these two alkaloids.



—Prof. Henry Wurtz corrects an error in the theory of A. McDougall, of the Manchester Literary and Philosophical Society, on the possible mode of formation of graphite, as given in our Notes for last month. As he points out, the carbon which collects in gas-retorts does not give the reactions of graphite with a mixture of chlorate of potassium and nitric acid; it is not converted into graphitic acid; therefore it is not graphite at all, and of course its formation cannot explain the formation of that mineral. It has even been shown by Berthelot that gas-retort carbon contains hydrogen, being in fact a highly-condensed hydro-carbon, or mixture of hydro-carbons.

Aniline Manufacturing Company, of Berlin, are now producing aniline colors by Coupler's process, in which no arsenic acid is employed. Being free from arsenic, these dyes are not only fitted for coloring sweet-meats, liqueurs, syrups, and pharmaceutical preparations, but may be used in many other industrial purposes where poisonous colors would be more or less dangerous, as in the staining of paper, paper-hangings, toys, etc.

burning in condensed air gradually increases in brilliancy with the compression, till at last it becomes as brilliant as the flame of phosphorus in oxygen. But, if the pressure be still further increased, the process of combustion is retarded, and the flame becomes smoky. From this it would appear that the temperature of combustion increases with the pressure up to the point of dissociation of the hydro-carbon gases of the candle. Hence the conclusion that it is an error to estimate the temperature of the sun at several millions of degrees. Sainte-Claire Deville holds that 2,000° C. is the highest possible temperature.

the distinguished African traveler, has been appointed by the Khédive Director-General of all the large collections, museums, and other scientific institutions, of Cairo.