Page:Popular Science Monthly Volume 14.djvu/383

Rh from evaporation by superincumbent watch-glasses with greased edges (Fig. 3).

In most instances the drops were absorbed entirely, leaving no traces of the mineral matter; in some cases a slight residue was left, which the addition of a minute quantity of water caused to disappear. As in the case of pure water, the under side of the leaves absorbed much more rapidly than the upper side. Solutions of sulphate and nitrate of potassium gave quite similar results; the absorption of solutions of chloride of sodium and nitrate of ammonium was not so perfect. These results would tend to show that the foliage of a plant is able to supply it with perhaps no small portion of its saline constituents by means of the ammoniacal salts formed in the air, and the alkaline and earthy salts suspended there which are deposited on the surface of the leaves by rain and dew.—Nature.

 

T is almost three centuries since Sir Walter Raleigh, after the discovery of Guiana, brought to Europe some arrows poisoned with a substance called by him curari. This poison was then in general use among the tribes inhabiting the Atlantic slope of South America. To-day we must penetrate into the depths of the forests to find the remnants of the ancient populations who possess the recipe for preparing curari. It may safely be affirmed that by next century it will have disappeared, either through the annihilation of these races, who are vanishing before the whites, or blending with them by intermarriage, or, above all, because firearms, obtained by way of barter from European traders, are steadily superseding the ancient implements of war and of the chase.

The arrow-poison is usually prepared from a substance often called veneno by the Spanish-Americans, and which occasionally happens to be brought to Europe under the name of curari. This substance, which the natives carry about in little earthenware pots or in calabashes, is a black, solid extract, with glistening fracture, in appearance very much like the black, inspissated juice of licorice. The active principle of curari is soluble in water, alcohol, blood, and all animal fluids; it is mixed with many impurities, which remain suspended in the solution, and among which the microscope detects vegetable débris, cells, and fibres. Ether and spirits of turpentine precipitate the curari poison, and in this way Messrs. Boussingault and Roulin have been able to isolate the active principle of curari, which they call 