The first situations in which the pointed arch was substituted for the semicircle are the wide spanning arches of vaulting and the arches carrying central towers and gables. We next find it in the wide arches of nave arcades; and it is not, as a general rule, till it became customary in those positions where it was demanded for practical reasons, that it began to be used as a matter of taste in other positions. Having secured the first object--an arch of reduced pressure--the second, viz., the abutment of an increased resistance, was attained by the systematic development of the buttress--a feature very much neglected by the Romanesque builders; and, as the vaulting of a lofty nave could not be directly supported by the ordinary buttress, the arched or flying buttress was introduced, spanning the aisles and conveying the pressure to the buttresses beyond. That this was introduced for utility only, and not from taste, is proved by the attempts in early instances to conceal it; so that we may with certainty conclude that all these beautiful features of Gothic architecture originated not from taste or caprice, but from reasoning upon practical and urgently pressing constructional requirements, and that the beauties to which they gave rise proceeded from the application to them of the great principle of Gothic architecture, the decoration of constructive or useful features. Let us, however, suppose for a moment that our building is not vaulted, but has timber roofs; there still remains an advantage in the use of the pointed arch. If it has, for instance, a central tower, the demand for an arch of reduced thrust is still greater than if the church had been vaulted, for the arms of the cross, from their reduced weight, are less effective as abutments.