THE INTERIOR OF THE EARTH. 461 



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 reestab- 

 lished, 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 for- 

 mation 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 con- 

 sidering 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 sur- 

 prising 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 

 en^a^ement for five hours without replenishing its ammunition, con- 

 tains less powder in its magazine than before the combat." Again, M. 

 Chai-les Sainte-Claire Deville, in his lectures at the College of France, 

 cited, in opposition to the uniformity theory, some considerations bor- 

 rowed 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 indefi- 

 nite 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 fur- 

 nished 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 Natu- 

 ralium"), 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. 



