The next quality I will mention is the extraordinary facility of our style in _decorating construction_, and in converting structural and useful features into elements of beauty. The arch, its normal feature, supplies to it an endless store of beauty. The vault supplies another inexhaustible fund, and assumes forms unrivalled in any other style. The window, comparatively neglected by the ancient architects, and even hated by the Greeks, was, in the hands of the Gothic builders, a perfect treasury of architectural loveliness; and the introduction of window-glass, an invention nearly unknown to the ancients, became the source of an entirely new and most enchanting art, and one which exercised the most surprising influence upon architecture. The buttress, the natural but unpromising accompaniment of an arcuated style, became in their magic hands, a source of stateliness and varied beauty. The roof, unwillingly shown by the Classic builders, adds solemn dignity to the works of their Northern successors; while, if need be, its timbers are made to contribute liberally to the effect of the interior. The campanile, a structure resulting wholly from practical necessity, became the greatest ornament of Christian cities, and supplied an endless variety of majestic forms, which had no parallels in ancient architecture; and generally, whatever feature, whether homely or otherwise, construction or utility demanded, was at once enlisted, and that with right goodwill and heartiness, among the essential elements of the design. Carrying out the same spirit, no material was either too rich or too rustic to find an honourable place in the works of these truly Catholic builders. The varied marbles of the Appenines, the polished amethysts of Bohemia, the glass mosaics of the Byzantines, with gold and silver, enamel, brass, and iron, were all brought under tribute to make their richer works glorious; yet they were equally at home in the use of brick, or flint, or rubble, and did not despise even a homely coating of plaster, if only it were honestly and truthfully used. And, what is more remarkable, they excelled in the use of nearly every one of these materials, and varied their design with instinctive precision to meet every one of their individual conditions. Carrying on the same spirit a step further, Gothic architecture shapes itself instinctively to varied climate and local tradition, and that without sacrificing its leading principles. It is true that its great normal types are found in Northern Europe, and that the north of France may, perhaps, be considered as its central province; yet how admirably does it shape itself to the varied conditions of Italy or Spain, to the valleys of Switzerland or the inhospitable shores of Scandinavia! while in every country where it prevailed it assumes a national type, and in every province a local variety.