27. THE POTATO.--The common or Irish potato is the vegetable most extensively used in this country and Great Britain. Among the poorer classes in Ireland it is the main article of food. While it is not so rich in nutritious substances as many others, it has some very useful qualities. It keeps well from season to season, and men do not weary of its continuous use. It is more than two-thirds water, the balance being chiefly starch, with a little albumen. [Sidenote: 28. Sweet potato? Nightshades? Potatoes when germinating?] 28. The sweet potato differs from the white or common, in containing more water and a small proportion of sugar. The common potato and the tomato belong to the same botanical order as the "nightshades," but do not possess their poisonous qualities, unless we except potatoes that are in the process of germination or sprouting, when they are found injurious as food. [Sidenote: 29. Fruits? Use of ripe fruit? Nutriment they contain? Starch in unripe fruits? Cooking of unripe fruits?] 29. FRUITS.--These are produced, in this country, in great abundance, and are remarkable alike for their variety and delicious flavor; consequently they are consumed in large quantities, especially during the warmer months. The moderate use of ripe fruits, in their season, is beneficial, because they offer a pleasant substitute for the more concentrated diet that is used in cold weather. The amount of solid nutriment they contain is, however, small. The percentage of water in cherries is seventy-five, in grapes eighty-one, in apples eighty-two. Unripe fruits contain starch, which, during the process of ripening, {74} is converted into sugar. Such fruits are indigestible and should be avoided: cooking, however, in part removes the objections to them. [Sidenote: 30. How should drinking-water be as regards color and smell? Chemically pure water? How obtained? Agreeableness of perfectly pure water?] 30. PURE WATER.--It is important that the water we drink and use in the preparation of food should be pure. It should be clear and colorless, with little or no taste or smell, and free from any great amount of foreign ingredients. Chemically pure water does not occur in nature: it is only obtained by the condensation of steam, carefully conducted, and is not as agreeable for drinking purposes as the water furnished by springs and streams. Rain-water is the purest occurring in nature; but even this contains certain impurities, especially the portion which falls in the early part of a shower; for in its descent from the clouds, the particles floating in the air are caught by the falling drops. [Sidenote: 31. Spring and well water? Whence the sparkle, or life? The water supply of cities? Croton water? Ridgewood?]