2233. The bridge is one of the grandest decorations of garden-scenery, where really useful. None require so little architectural elaboration, because every mind recognises the object in view, and most minds are pleased with the means employed to attain that object in proportion to their simplicity. There are an immense variety of bridges, which may be classed according to the mechanical principles of their structure, the style of architecture, or the materials used. With respect to the principles of their mechanical structure, the materials of bridges are held together, either by their gravity, as in all arches, whether of stone, iron, or timber; or by their tenacity, as in single planks, flat bridges of iron or timber, and those new and wonderful exertions of ingenuity, suspended bridges, of which fine examples have been executed across the Menai and the Tweed, and the principles of which we have elsewhere (Annals of Philosophy, Jan. 1816) entered into at large. With respect to styles of architecture, the bridge affords little opportunity of detailed display; but the openings may be circular or pointed arches, or right-lined, or a mixture of these. As to material, bridges of tenacity are formed of timber or wrought iron; bridges of gravity, generally of cast iron or stone; but they may be formed of any material.
