Material must depend much upon locality, but iron is undoubtedly to hold an important place in our architecture. Already it is extensively used, but does not seem to command general favor. The reason is that nearly everything that has been done with it so far is not iron architecture, but stone architecture done in iron. We do not let it speak its own language; the truss, the tie rod, and the girder are kept out of sight, while every possible display is made of consoles and cornices and Corinthian columns and balustrades, and all sorts of foreign expressions. No wonder that it is unable to give an account of itself with all these false witnesses. Stone houses should be made of stone, and if made of wood or iron or plaster, they are nothing but shams, unenduring and unsatisfactory. Now architecture requires the least amount of material that is compatible with the greatest amount of strength. The forms of different materials must be varied to suit their texture, according as it is fibrous or crystalline, tough or brittle. Iron, of course, requires a peculiar treatment. At the risk of being charged with pedantry, we say that there have never been but two iron buildings, of any pretension, in this country--the Niagara Suspension Bridge and the Crystal Palace at New York. The first still speaks for itself; and of the latter, no one who saw it can forget what an exquisite structure it was, so light and airy and elegant, and yet so strong. It was but a bird cage, though, compared with its enormous prototype at Sydenham. That is unquestionably one of the wonders of the world; its internal _coup d'oeil_ is without a parallel. Fancy a broad level vista, a third of a mile long, flanked on either side by graceful groves of ironwork, and covered with a continuous crystal arch, a hundred feet above your head; line it with a profusion of tropical foliage and clambering vines, that grow as luxuriantly as in their native woods, and interspersed with statuary and vases gleaming everywhere through the rich masses of verdure, while here and there fountains of rare and exquisite design, rising from broad marble basins, relieve without lessening the immense length--and you may have some faint idea of this peerless structure. 'No material is used in it,' says Fergusson, 'which is not the best for its purpose, no constructive expedient employed which was not absolutely necessary, and it depends wholly for its effect on the arrangement of its parts and the display of its construction.' It is in iron what Gothic is in stone.