“Such might be the reasoning of one who casts a superficial and indifferent glance upon the external world. But the conclusions of one accustomed to scrutinize closely the apparently insignificant changes taking place about him would be quite different. At every step, however little skilled in observation, he will discover the traces of a perpetual conflict between the external powers of nature and all which rises above the inflexible level of the ocean, in whose depths reign silence and repose. Here, the sea beats furiously against the shore, which recedes slowly from century to century. Elsewhere, mountain masses have fallen, engulfing in a few moments entire villages and desolating smiling valleys. Or, the tropical rains, assailing the volcanic cones, have furrowed them with deep ravines and undermined their walls, so that at last nothing but ruins of these giants remain.
“More silent, but not less efficacious, has been the action of the great rivers, as the Ganges and the Mississippi, whose waters are so heavily laden with solid particles in suspension. Each of these small particles, which trouble the limpidity of their liquid carrier, is a fragment torn from the shores washed by these rivers. Slowly but surely their currents bear to the great reservoir of the sea every atom lost to the soil, and the bars which form their deltas are as nothing compared with what the sea receives and hides away in its abysses. How can any reflecting person, observing this action, and knowing that it has been going on for many centuries, escape the conclusion that the rivers, like the ocean, are indeed preparing the final ruin of the habitable world?
“Geology confirms this conclusion in every particular. It shows us that the surface of the soil is being constantly altered over entire continents by variations of temperature, by alterations of drought and humidity, of freezing and thawing, as also by the incessant action of worms and of plants. Hence, a continuous process of dissolution, leading even to the disintegration of the most compact rocks, reducing them to fragments small enough to yield at last to the attraction of gravity, especially when this is aided by running water. Thus they travel, first down the slopes and along the torrent beds, where their angles are worn away and they become little by little transformed into gravel, sand and ooze; then in the rivers which are still able, especially at flood-times, to carry away this broken up material, and to bear it nearer and nearer to their outlets.
“It is easy to predict what must necessarily be the final result of this action. Gravity, always acting, will not be satisfied until every particle subject to its law has attained the most stable position conceivable. Now, such will be the case only when matter is in the lowest position possible. Every surface, must therefore disappear, except the surface of the ocean, which is the goal of every agency of motion; and the material borne away from the crumbling continents must in the end be spread over the bottom of the sea. In brief, the final outcome will be the complete levelling of the land, or, more exactly, the disappearance of every prominence from the surface of the Earth.
“In the first place, we readily see that near the river mouths the final form of the dry land will be that of nearly horizontal plains. The effect of the erosion produced by running water will be the formation on the watersheds of a series of sharp ridges, succeeded by almost absolutely horizontal plains, between which no final difference in height greater than fifty meters can exist.
“But in no case can these sharp ridges, which, on this hypothesis, will separate the basins, continue long; for gravity and the action of the wind, filtration and change of temperature, will soon obliterate them. It is thus legitimate to conclude that the end of this erosion of the continents will be their reduction to an absolute level, a level differing but little from that at the river outlets.”
The coadjutor of the archbishop of Paris, who occupied a seat in the tribune reserved for distinguished functionaries, rose, and, as the orator ceased speaking, added: “Thus will be fulfilled, to the letter, the words of holy writ: ‘For the mountains shall depart and the hills be removed.’ ”
“If, then,” resumed the geologist, “nothing occurs to modify the reciprocal action of land and water, we cannot escape the conclusion that every continental elevation is inevitably destined to disappear.
“How much time will this require?
“The dry land, if spread out in a layer of uniform thickness, would constitute a plateau of about 700 meters altitude above the sea-level. Admitting that its total area is 145,000,000 square kilometers, it follows that its volume is about 101,500,000, or, in round numbers, 100,000,000 cubic kilometers. Such is the large, yet definite mass, with which the external agencies of destruction must contend.
“Taken together, the rivers of the world may be considered as emptying, every year, into the sea 23,000 cubic kilometers of water (in other words, 23,000 milliards of cubic meters). This would give a volume of solid matter carried yearly to the sea, equal to 10.43 cubic kilometers, if we accept the established ratio of thirty-eight parts of suspended material in 100,000 parts of water. The ratio of this amount to the total volume of the dry land is
