The alcoholic contents of a cask extract from the wood a certain quantity of matter soluble in alcohol of that strength. Among the substances extracted from the wood are tannin, and, to a considerable extent, the acids, which are contained in the wood. There is also a considerable quantity of coloring matter found in solution. The whisky in wood, during the process of ageing, gradually acquires, more or less, a red color. The matters extracted from the wood cannot be without effect upon the whisky, and a certain taste is given to the whisky, as well as flavor and aroma, from the extract of the wood itself. The matters extracted from the wood, although they may be pleasant to the nostrils and the palate are not the things valuable in whisky which give it its characteristic flavor. There are certain chemical changes which take place in the spirits, such as blending and mellowing, due to the chemical reactions of the constituents minute in quantity, and yet of great significance. The final result is an increase in aromatic ethers and acids.