A. Its value, as a means of producing food and mechanical power, varies with its form (as mountain or plain), with its substance (in soil or mineral contents), and with its climate. All these conditions of intrinsic value, in order to give effectual value, must be known and complied with by the men who have to deal with it; but at any given time, or place, the intrinsic value is fixed; such and such a piece of land, with its associated lakes and seas, rightly treated in surface and substance, can produce precisely so much food and power, and no more. Its surface treatment (agriculture) and substance treatment (practical geology and chemistry), are the first roots of economical science. By surface treatment, however, I mean more than agriculture as commonly understood; I mean land and sea culture;--dominion over both the fixed and the flowing fields;--perfect acquaintance with the laws of climate, and of vegetable and animal growth in the given tracts of earth or ocean, and of their relations regulating especially the production of those articles of food which, being in each particular spot producible in the highest perfection, will bring the best price in commercial exchanges. B. The second element of value in land is its beauty, united with such conditions of space and form as are necessary for exercise, or pleasant to the eye, associated with vital organism. Land of the highest value in these respects is that lying in temperate climates, and boldly varied in form; removed from unhealthy or dangerous influences (as of miasm or volcano); and capable of sustaining a rich fauna and flora. Such land, carefully tended by the hand of man, so far as to remove from it unsightlinesses and evidences of decay; guarded from violence, and inhabited, under man's affectionate protection, by every kind of living creature that can occupy it in peace, forms the most precious "property" that human beings can possess. The determination of the degree in which these two elements of value can be united in land, or in which either element must, or should, in particular cases, be sacrificed to the other, forms the most important branch of economical inquiry respecting preferences of things. 2. Buildings, furniture, and instruments. The value of buildings consists--A, in permanent strength, with convenience of form, of size, and of position; so as to render employment peaceful, social intercourse easy, temperature and air healthy. The advisable or possible magnitude of cities and mode of their distribution in squares, streets, courts, etc., the relative value of sites of land, and the modes of structure which are healthiest and most permanent, have to be studied under this head. B. The value of buildings consists, secondarily, in historical association and architectural beauty, of which we have to examine the influence on manners and life. The value of instruments consists--