In discussing the great wood structures such as screens, house fronts, roofs, and other large pieces of mechanism, which developed in boldness and variety in the fifteenth century, we must not forget that the abundance of oak timber in the north of Europe both suggested much of this timber art and admitted of bold features of construction from the size of the logs and the tenacity of the material. A large portion of England and perhaps an equal proportion of Ireland were covered with dense forests of oak. The eastern frontier of France, great portions of Burgundy, and many other districts in France, Germany, Flanders, and other northern countries, were still forests, and timber was to be had at low prices and in any quantity. Spanish chestnut had been introduced probably by the Romans into England. Though churches, castles, and manors were built of stone or brick, or both, yet whole cities seem to have been mainly constructed out of timber. The London of the fifteenth century, like a hundred other cities, though abounding in noble churches and in great fortified palaces, yet presented the aspect of a timber city. The houses were framed together, as a few still are in some English towns and villages, of vast posts sixteen to twenty-four inches square in section, arching outwards and meeting the projecting floor timbers, and so with upper stories, till the streets were darkened by the projections. The surfaces of these posts were covered with delicate tracery, niches and images. In the streets at Chester an open gallery or passage is left on the first floor _within_ the timbers of the house fronts. In the court of St. Mary's guild in Coventry, whole chambers and galleries are supported on vast arches of timber like bridges. Oriels jutted out under these overhanging stories, and the spaces between the framing posts were filled in, sometimes with bricks, sometimes with laths and mortar, or parts (as the century wore on) more frequently with glass. In London and Rouen, in Blois and in Coventry, these angle posts were filled with niches and statuettes or fifteenth century window tracery sunk into the surfaces. The dark wooden houses were externally a mass of imagery. In the great roofs of these centuries, such as the one spoken of at Westminster, the hammer beams were generally carved into figures of angels gracefully sustaining the timber behind them with outstretched wings; and these figures were painted and gilt. A magnificent example remains intact in the church of Knapton in Norfolk. [Illustration]