This style of architecture is popularly known as Perpendicular, but as the horizontal lines are quite as distinct a feature as are the vertical, it would perhaps be more correct to speak of it as Rectilinear. This change in architectural form made its appearance towards the close of the XIVth century, although it was by no means generally introduced at that period, for the old methods and styles were carried on side by side with the new for many years. For example, the eastern end of the choir of York Minster (1361-99) possesses a window the traceries of which contain both curvilinear and rectilinear lines, while Shottesbrook Church in Berkshire (1387), and Wimmington Church, Bedfordshire (1391) are examples of village churches neither of which has any feature of the Perpendicular style. [Illustration: Yeovil Parish Church (A.D. 1376). Early Perpendicular in style, without a clerestory, and called, for its large window area, the "Lantern of the West."] In its earlier stages the Perpendicular style presented an effect at once good and bold; the mouldings, though not equal to the best of the Decorated style, were well defined, the enrichments effective, and the details delicate without extravagant minuteness. Subsequently the style underwent a gradual debasement; the arches became depressed; the mouldings impoverished, the details crowded and coarsely executed, and the whole style became wanting in the chaste and elegant effects for which the Decorated stands unapproached and unapproachable. The flowing contours and curved lines of the previous style now gave place in the windows to mullions running straight up from the bottom to the top, and crossed by transoms. As the arch became more and more depressed the mouldings became shallower and less effective. In early buildings of this period the drop arch is very prevalent, but as the period advanced a form known as the Tudor arch began to be used. It is an arch in which, as a rule, the centres of the upper portion lie immediately below those of the lower, but this is not always the case. Sometimes the whole of the upper portion uniting the arcs of the ends is struck from one centre, in which case the arch becomes a three-centred one, being, in fact, half an ellipse. Towards the close of the style the curvature of the upper portion is so slight that it can hardly be distinguished from a straight line, and as the debasement progressed it became really straight. Ogee arches are also found at this period, and foiled arches are very frequent. When the Tudor arch was not used, we generally find the low drop arch, these three last being mostly used for small openings. [Illustration: A Fine Parish Church showing Rich Perpendicular Work. Terrington St. Clement, Norfolk. _Photograph Dexter & Son._] The peculiar characteristics of the windows--the perpendicular mullions and horizontal transoms--we have already alluded to. [Side note: Perpendicular Windows.]