upon a tract of granite, such agents here work scarcely an appreciable effect; there cause exfoliations of the surface, and a resulting heap of _débris_ and boulders; and elsewhere, after decomposing the feldspar into a white clay, carry away this with the accompanying quartz and mica, and deposit them in separate beds, fluviatile and marine. When the exposed land consists of several unlike formations, sedimentary and igneous, changes proportionably more heterogeneous are wrought. The formations being disintegrable in different degrees, there follows an increased irregularity of surface. The areas drained by different rivers being differently constituted, these rivers carry down to the sea unlike combinations of ingredients; and so sundry new strata of distinct composition arise. And here indeed we may see very simply illustrated, the truth, that the heterogeneity of the effects increases in a geometrical progression, with the heterogeneity of the object acted upon. A continent of complex structure, presenting many strata irregularly distributed, raised to various levels, tilted up at all angles, must, under the same denuding agencies, give origin to immensely multiplied results: each district must be peculiarly modified; each river must carry down a distinct kind of detritus; each deposit must be differently distributed by the entangled currents, tidal and other, which wash the contorted shores; and every additional complication of surface must be the cause of more than one additional consequence. But not to dwell on these, let us, for the fuller elucidation of this truth in relation to the inorganic world, consider what would presently follow from some extensive cosmical revolution—say the subsidence of Central America. The immediate results of the disturbance would themselves be sufficiently complex. Besides the numberless dislocations of strata, the ejections of igneous matter, the propagation of earthquake vibrations thousands of miles around, the loud explosions, and the escape of gases, there would be the rush of the Atlantic and Pacific Oceans to supply the vacant space, the subsequent recoil of enormous waves, which would traverse both these oceans and produce myriads of changes along their shores, the corresponding atmospheric waves complicated by the currents surrounding each volcanic vent, and the electrical discharges with which such disturbances are accompanied. But these temporary effects would be insignificant compared with the permanent ones. The complex currents of the Atlantic and Pacific would be altered in directions and amounts. The distribution of heat achieved by these currents would be different from what it is. The arrangement of the isothermal lines, not only on the neighbouring continents, but even throughout Europe, would be changed. The tides would flow differently from what they do now. There would be more or less modification of the winds in their periods, strengths, directions, qualities.