A third and a very important feature of the Gothic order is the use of the arch. The much-increased constructive power of which we have spoken depended very largely upon this. The ancients knew the use of the arch, but did not like it because they thought that it took away from the repose of a building. Even now the Hindoos will not use it; they say, "An arch never sleeps," and though the Mohammedan builders have used it in their country, the Hindoos cannot overcome their dislike of it. In the Gothic order, however, the use of arches, both round and pointed, is unending. The results are very much varied, and range all the way from a grand and impressive effect to a sort of toy-like lightness which seems more suited to the block-houses made by children than to the works of architects. The earlier Gothic arches were round, although pointed arches are occasionally found in very ancient buildings. The picture (Fig. 71), however, gives a just idea of the form of arch most used until the introduction of the pointed arch, which occurred in France during the twelfth century. Of this form the doorways of the next cut present a fine example (Fig. 72). [Illustration: FIG. 72.--FAÇADE OF CATHEDRAL OF NOTRE DAME. _Paris._] [Illustration: FIG. 73.--CLUSTERED PILLAR.] [Illustration: FIG. 74.--BUTTRESS.] [Illustration: FIG. 75.--HINGE.] [Illustration: FIG. 77.--IRON-WORK.] [Illustration: FIG. 78.--GARGOYLE.] [Illustration: FIG. 76.--NAIL-HEAD.] [Illustration: FIG. 79.--SCROLL.] An important characteristic of Gothic architecture was the fact that every part of the building was so made as to show its use. Instead of hiding the supports they were made prominent. If a pier or buttress was to stand a perpendicular strain, even the lines of decoration were generally made to run in that direction; if extra supports were needed, they were not concealed, but built in so as to show, and even to be prominent. In the details the same feeling was often shown in a very marked degree; the hinges and nails and locks of Gothic buildings were made to be seen, and whatever was needed for use was treated as if it were of value as an ornament. The spouts by which the water was carried over the eaves were made bold and comparatively large, and carved into those curious shapes of animals and monsters called gargoyles, which are seen on so many mediæval edifices. Many of these details of Gothic buildings are very elegant, and serve to-day as models for modern workmen. (See Figs. 73, 74, 75, 76, 77, 78, 79.) Among the inventions of Gothic architects the division of the interior into three aisles, with the centre one much the highest, was very important. By this arrangement the space was made to appear longer and higher than it really was, and what was lost in the effect of width was more than made up in a certain elegance of form which is very pleasing. The three central aisles of the next cut illustrate this arrangement (Fig. 80).