Seventeenth-century houses in colonial North American were simple structures that were primarily functional, carrying over traditional designs that went back to the Middle Ages.  During the first half of the eighteen century, however, houses began to show a new elegance.  As wealth increased, more and more colonist built fine houses.    Since architecture was not yet a specialized profession in the colonies, the design of buildings was left either to amateur   designers or to carpenters who were engaged in translating architectural handbooks imported from England.  Inventories of libraries shows an astonishing number of these handbooks for builders, and the houses built during the eighteenth century show their influence.  Nevertheless, most household architecture of the first-quarters of the eighteenth century displays a wide  _ of taste and freedom of application of the rules laid down in these books.    Increasing wealth and growing sophistication   throughout the colonies resulted in houses of improved design, whether the material was wood, stone, or brick.  New England still favored wood, though brick houses became common in Boston and other towns, where the danger of fire gave an impetus   to the use of more durable material.  A few houses in New England were built of stone, but only in Pennsylvania and areas nearby was stone widely used in buildings.  An increased use of brick in houses and outbuildings is noticeable in Virginia and Maryland, but wood remained the most popular material even in houses built by wealthy landowners.  In the Carolinas, even in closely packed Charleston, wooden houses were much common than brick houses.    Eighteenth-century houses showed great interior improvements over the former ones.  Windows were made larger and shutters removed.  Large, clear panes replaced the small leaded glass of the seventeenth century.  Doorways were larger and more decorative.    Fireplaces became decorative features of rooms.  Walls were made of plaster or wood.  White paint began to take the place of blues, yellows, greens, and lead color1s, which had been popular for walls in the earlier years.  After about 1730, advertisements for wallpaper styles in scenic patterns began to appear in colonial newspapers. What's the passage mainly about?
The improved design of eighteenth-century colonial houses. A comparison of eighteenth-century houses and modern houses. The decorations used in eighteenth-century houses. The role of carpenters in building eighteenth-century houses.