A disregard of these rules gives one the rank, black, unpleasant infusion too often offered as tea; while, if boiled in tin, it becomes a species of slow poison,--the tannic acid in the tea acting upon the metal, and producing a chemical compound whose character it is hard to determine. Various other plants possess the essential principle of tea, and are used as such; as in Paraguay, where the Brazilian holly is dried, and makes a tea very exhilarating in quality, but much more astringent.
The use of _Coffee_ dates back even farther than that of tea. Of the many varieties, Mocha and Java are finest in flavor, and a mixture of one-third Mocha with two-thirds Java gives the drink at its best. As in tea, there are three chief constituents: (1) A volatile oil, giving the aroma it possesses, but less in amount than that in tea. (2) Astringent matter,--a modification of tannin, but also less than in tea. (3) Caffeine, now found identical with theine, but varying in amount in different varieties of coffee,--being in some three or four per cent, in others less.
The most valuable property of coffee is its power of relieving the sensation of hunger and fatigue. To the soldier on active service, nothing can take its place; and in our own army it became the custom often, not only to drink the infusion, but, if on a hard march, to eat the grounds also. In all cases it diminishes the waste of tissue. In hot weather it is too heating and stimulating, acting powerfully upon the liver, and, by producing over-activity of that organ, bringing about a general disturbance.
So many adulterations are found in ground coffee, that it is safest for the real coffee-lover to buy the bean whole. Roasting is usually more perfectly done at the grocers', in their rotary roasters, which give every grain its turn; but, by care and constant stirring, it can be accomplished at home. Too much boiling dissipates the delicious aroma we all know; and the best methods are considered to be those which allow no boiling, after boiling water has been poured upon it, but merely a standing, to infuse and settle. The old fashion, however, of mixing with an egg, and boiling a few minutes, makes a coffee hardly inferior in flavor. In fact, the methods are many, but results, under given conditions, much the same; and we may choose urn, or old-fashioned tin pot, or a French biggin, with the certainty that good coffee, well roasted, boiling water, and good judgment as to time, will give always a delicious drink. Make a note of the fact that long boiling sets free tannic acid, powerful enough to literally tan the coats of the stomach, and bring on incurable dyspepsia. Often coffee without milk can be taken, where, with milk, it proves harmful; but, in all cases, moderation must rule. Taken too strong, palpitation of the heart, vertigo, and fainting are the usual consequences.
