The water from rivers flowing past large cities and villages is often so impure as to render its use decidedly deleterious, if not an actual source of disease. In some cases they have been literally so filled with portions of fish, and other animal matter, that all city supplies were made endurable only by long-continued filtration. The waters of many of our Southern and Western rivers are rendered impure from the lime and surface drainage with which they are so highly impregnated that they often become a direct source of diarrhoea and cholera. Pure water, free from the impregnation of vegetable, animal and mineral substances, should be sought and obtained for domestic use. A good nutritious diet is an indispensable requisite in the prevention of disease. The system in comparative health requires, and should regularly receive, its proper aliment. Its daily recurring demands should be judiciously met with pure and wholesome food, in such quantity as can be readily digested, assimilated and duly appropriated for the supply of its wants. Due regard, however, must be had to the existing and peculiar condition of the digestive organs, on which mainly depends the process of supporting and perpetuating the general health. It is not the profuse variety and the incongruous mass composed of baked, roasted, boiled and fried meats, fish and fowl, oyster, lobster, frog and turtle, with puddings, tarts, jellies, cakes and creams from the pastry room--fruits and salads, native and foreign, rich and rare--alcoholic stimulants, and cooling ices, but the simple, plain and frugal diet, properly cooked and particularly nutritious, that conduces to the most vigorous health. Regular, temperate habits in all things, are especially commended; excesses of all kinds are reprehensible. Great and sudden changes in the habits of living are always deleterious, and must be particularly so, when an appalling and fatal epidemic is prevailing. Temperance, sobriety and cheerfulness, regular hours for meals, for rest and for business, repeated ablutions and perfect cleanliness, moderate exercise and avoidance of irregularities, persevering self-government and duly subjected passions, all contribute to health, to happiness, and the prevention of disease. Exposure to the extremes of heat and cold should be avoided, and the clothing properly adapted to the climate--to the season and its variable temperature. Constant vigilance is necessary to guard against the numberless causes tending to produce an abnormal condition, resulting in the derangement of the stomach and bowels, or in depressing the nervous power, thus enfeebling and prostrating the general health. The neglect of these hygienic principles and essential preventives of cholera may induce the condition which temptingly invites the disease. Some are vastly more susceptible than others, and may not be able, with all their watchfulness and care, to avoid an attack, should the disease extensively prevail among us.