In architecture, and all those arts in which ornamental forms are given to solid materials, the binocular camera and the stereoscope will be found indispensable. The carvings of ancient, or mediæval, or modern art may be copied and reproduced in relief, whatever be the material from which they have been cut. The rich forms of Gothic architecture, and the more classical productions of Greek and Roman genius, will swell the artist’s portfolio, and possess all the value of casts. With the aid of the Kaleidoscope the modern artist may surpass all his predecessors. He may create an infinite variety of those forms of symmetry which enter so largely into the decorative arts; and if the individual forms, which constitute the symmetrical picture, are themselves solid, the binocular-kaleidoscopic pictures, taken photographically, will be raised into the original relief of their component parts, or they may be represented directly to the eye in relief, by semi-lenses placed at the ocular extremities of the reflecting plates.[64] If the symmetrical forms are taken from lines in the same plane, no relief will be obtained from the kaleidoscopic pictures. [64] See my Treatise on the Kaleidoscope, second edition, just published. But it is not merely to the decorative parts of architecture that the stereoscope is applicable. The noblest edifices, whether of a civil, a religious, or a military character, which he could otherwise study only as a traveller, and represent in hurried and imperfect sketches, will, when taken binocularly, stand before him in their full relief and grandeur, reflecting to his eye the very lights and shadows which at a given hour the sun cast upon their walls. In the erection of public buildings, hourly or daily photographs have been taken of them, to shew to the absent superintendent the progress of his work; but these pictures will be still more expressive if binocular ones are combined in the stereoscope. To the engineer and the mechanist, and the makers of instruments of all kinds, the stereoscope will be of inestimable value. The difficulty of representing machinery is so great that it is not easy to understand its construction or its mode of operation from plans and perspective views of it. The union of one or two binocular pictures of it, when thrown into relief, will, in many cases, remove the difficulty both of drawing and understanding it. Photographs of machinery, however, consisting of a number of minute parts at different distances from the eye, have, when taken by large lenses, all the defects which we explained in reference to trees and their branches and leaves. Supports and axles will be transparent, and the teeth of the wheels, and the small and distant parts of the mechanism, will be seen through all the nearer parts whose width is less than the diameter of the lens.