Page:Popular Science Monthly Volume 17.djvu/477

Rh folding back and elevating the edges, and forming, as it solidifies, long ridges which constitute the mountain-chains. The waters, displaced from their old beds, seek new basins, and, as a state of calm is reestablished, they deposit the matter with which they become charged during the period of disturbance; and it is thus that sedimentary deposits, spreading over the more ancient disruptions, are formed. The existing configuration of the surface would thus be the resultant of a series of elevations separated by long intervals of time. The chronology of these occurrences M. de Beaumont has endeavored to establish by the aid of geometric laws, by virtue of which chains of contemporary formation assume a parallel direction. This theory of mountain upheavals has its weak features, especially that relating to the synchronism of its formations. It has been vigorously combated by the Sir Charles Lyell school, which attributes all the changes of the earth's surface to the slow action of forces that are still in operation about us. In considering the prodigious effects of volcanic eruptions and earthquakes, the secular oscillations of the ground, the changes of the earth's surface even in our day by the action of the sea and of rivers, the partisans of uniformity in geological changes reject the theory of cataclysms, as held by the opposite school. Still, it can not be denied that the earth has grown old, and that its energy must have diminished. On this point Sir W. Thomson makes a judicious remark: "It might be surprising but strictly admissible to assert that volcanic activity as a whole has never been more intense than at the present time. But it is not less certain that the earth contains to-day a smaller store of volcanic energy than it did a thousand years ago, as a ship of war, after a sharp engagement for five hours without replenishing its ammunition, contains less powder in its magazine than before the combat." Again, M. Charles Sainte-Claire Deville, in his lectures at the College of France, cited, in opposition to the uniformity theory, some considerations borrowed from an article of M. J. Bertrand's, on similitude in mechanism, from which it appears impossible, in accounting for a displacement of a given magnitude, to compensate for a deficit in energy by an indefinite extension of the time employed.

There is thus no lack of argument drawn from geognosy to sustain the hypothesis that changes in the earth are attributable to the mobility of the liquid nucleus; but we now pass to an examination of those furnished by astronomy.

Emanuel Swedenborg left behind him as a souvenir only a theosophy and a thaumaturgy; he was, however, a distinguished engineer, and before becoming the leader of a sect of visionaries, as the assessor of the Stockholm College of Mines published some researches that are not without value. In his great work of 1734 ("Principia Rerum Naturalium"), to which M. Nyren has recently called the attention of the scientific world, is for the first time elaborated a theory of the universe closely resembling the celebrated cosmogonic hypothesis of Laplace.