Fragments, as well as entire roadways and arches of natural bridges, are more numerous in rocky, mountainous, and volcanic regions than is generally supposed; the action of the water in excavating cliffs, the segments of caverns, the, accidental shapes of geological formations, often result in structures so adapted for the use and like the shape of bridges as to appear of artificial origin. In the States of Alabama and Kentucky, especially, we have notable instances of these remarkable freaks of Nature: there is one in Walker County, of the former State, which, as a local curiosity, is unsurpassed; and one in the romantic County of Christian, in the latter State, makes a span of seventy feet with an altitude of thirty; while the vicinity of the famous Alabaster Mountain of Arkansas boasts a very curious and interesting formation of this species. Two of these natural bridges are of such vast proportions and symmetrical structure that they rank among the wonders of the world, and have long been the goals of pilgrimage, the shrines of travel. Their structure would hint the requisites, and their forms the lines of beauty, desirable in architectural prototypes. Across Cedar Creek, in Rockbridge County, Virginia, a beautiful and gigantic arch, thrown by elemental forces and shaped by time, extends. It is a stratified arch, whence you gaze down two hundred feet upon the flowing water; its sides are rock, nearly perpendicular. Popular conjecture reasonably deems it the fragmentary arch of an immense limestone cave; its loftiness imparts an aspect of lightness, although at the centre it is nearly fifty feet thick, and so massive is the whole that over it passes a public road, so that by keeping in the middle one might cross unaware of the marvel. To realize its height it must be viewed from beneath; from the side of the creek it has a Gothic aspect; its immense walls, clad with forest-trees, its dizzy elevation, buttress-like masses, and aerial symmetry make this sublime arch one of those objects which impress the imagination with grace and grandeur all the more impressive because the mysterious work of Nature,--eloquent of the ages, and instinct with the latent forces of the universe. Equally remarkable, but in a diverse style, is the Giant's Causeway, whose innumerable black stone columns rise from two to four hundred feet above the water's edge in the County of Antrim, on the north coast of Ireland. These basaltic pillars are for the most part pentagonal, whose five sides are closely united, not in one conglomerate mass, but, articulated so aptly that to be traced the ball and socket must be disjointed.