The complete triumph of the vertical tendency, foreshadowed in the Roman, was proclaimed in Gothic architecture in the use of the pointed arch. For in the round arch the vertical has not conquered after all; the horizontal is still active there, even to the apex of the arch, where the tangential line is parallel to the earth, the line of weight. But in the pointed style the victory of the vertical is clearly decisive,--the upward and inward forces, by elongating and narrowing the curve of the arch to a point, have dominated the downward and outward. The great height of the piers, the gabled roofs, the ribs of the vaults the pointed form of the windows, the towers, spires, and pinnacles,--all proclaim it. Yet this victory does not occur without opposition; for the higher the vaulting, the greater the weight to be carried; the greater, therefore, the outward thrust, which had to find its expression and its stay in the buttress. But even the buttress, although it bears witness to the outward and horizontal force of weight, was nevertheless so fashioned with its gable and pinnacle, or its own arched form, as to aid the upward movement. The thinness of walls and partitions, and the piercing of these with arches and windows, by lightening the force of weight, also contributed to increase the vertical movement. At sight of a true Gothic cathedral, we feel ourselves fairly lifted off the ground and rushed upward. In thinking of the beauty of architecture, we are all too apt to consider the exterior exclusively, forgetting that the inside of a building, where we live, is even more important practically, and is capable of at least as great an aesthetic effect. The characteristic aesthetic effect of the interior is a function of the inclosed space, the volume, not of the inclosing walls taken singly. The walls are only the limits of this space, they are not the space itself. Of course, the walls within have their own beauty, of surface and pervading energy, but this does not differ markedly from that of the walls seen from the outside, and what we have established for the one holds for the other. But the beauty of the inclosed space is something entirely new.