“It is easy to estimate the effect of this new factor. Indeed, for a given thickness lost by the plateau heretofore assumed, the sea-level must rise by an amount corresponding to the volume of the submarine deposit, which must exactly equal that of the sediment brought down. Calculation shows that, in round numbers, the loss in volume will be _twenty-four cubic kilometers_. “Having accounted for an annual loss of twenty-four cubic kilometers, are we now in a position to conclude what time will be necessary for the complete disappearance of the dry land, always supposing the indefinite continuance of present conditions? “Certainly, gentlemen; for, after examining the objection which might be made apropos of volcanic eruptions, we find that the latter aid rather than retard the disintegrating process. “We believe, therefore, that we may fearlessly accept the above estimate of twenty-four cubic kilometers, as a basis of calculation; and as this figure is contained 4,166,666 times in 100,000,000, which represents the volume of the continents, we are authorized to infer that under the _sole action of forces now in operation_, provided no other movements of the soil occur, _the dry land will totally disappear within a period of about 4,000,000 years_. “But this disappearance, while interesting to a geologist or a thinker, is not an event which need cause the present generation any anxiety. Neither our children nor our grandchildren will be in a position to detect in any sensible degree its progress. “If I may be permitted, therefore, to close these remarks with a somewhat fanciful suggestion, I will add that it would be assuredly the acme of foresight to build today a new ark, in which to escape the consequences of this coming universal deluge.” [Illustration: THE WATERS COVERING THE FACE OF THE EARTH. ] Such was the learnedly developed thesis of the president of the geological society of France. His calm and moderate statement of the secular action of natural forces, opening up a future of 4,000,000 years of life, had allayed the apprehension excited by the comet. The audience had become wonderfully tranquillized. No sooner had the orator left the platform and received the congratulations of his colleagues than an animated conversation began on every side. A sort of peace took possession of every mind. People talked of the end of the world as they would of the fall of a ministry, or the coming of the swallows—dispassionately and disinterestedly. A fatality put off 40,000 centuries does not really affect us at all. But the permanent secretary of the academy of meteorology had just ascended the tribune, and every one gave him at once the strictest attention: “Ladies and gentlemen: I am about to lay before you a theory diametrically opposed to that of my eminent colleague of the Institute, yet based upon facts no less definite and a process of reasoning no less rigorous. “Yes, gentlemen, diametrically opposed”—