Essay on the Theory of the Earth

by baron Georges Cuvier

However this may be, the establishment of man in those countries in which we have said that the fossil remains of land animals are found, that is to say, in the greatest part of Europe, Asia, and America, has necessarily been posterior, not only to the revolutions which have covered up these bones, but also to those which have laid bare the strata containing them, and which are the last that the globe has undergone. Hence it clearly appears, that no argument in favour of the antiquity of the human species in these different countries can be derived either from those bones themselves, or from the more or less considerable masses of rocks or of earthy materials by which they are covered.

Physical Proofs of the Newness of the Present Continents.

On the contrary, by a careful examination of what has taken place on the surface of the globe, since it has been laid dry for the last time, and its continents have assumed their present form, at least in the parts that are somewhat elevated, it may be clearly seen that this last revolution, and consequently the establishment of our existing societies, could not have been very ancient. This result is one of the best established, and, at the same time, one of the least attended to in rational geology; and it is so much the more valuable, that it connects natural and civil history in one uninterrupted series.

When we measure the effects produced in a given time by causes still acting, and compare them with those which the same causes have produced since they have begun to act, we are enabled to determine nearly the instant at which their action commenced; which is necessarily the same as that in which our continents assumed their present form, or that of the last sudden retreat of the waters.

It must, in fact, have been since this last retreat of the waters, that our present steep declivities have begun to disintegrate, and to form heaps of debris at their bases; that our present rivers have begun to flow, and to deposit their alluvial matters; that our present vegetation has begun to extend itself, and to produce soil; that our present cliffs have begun to be corroded by the sea; that our present downs have begun to be thrown up by the wind: just as it must have been since this same epoch, that colonies of men have begun, for the first or second time, to spread themselves, and to form establishments in places fitted by nature for their reception. I do not here take the action of volcanoes into account, not only because of the irregularity of their eruptions, but because we have no proofs of their not having been able to exist under the sea; and because, on that account, they cannot serve us as a measure of the time which has elapsed since its last retreat.

Additions of Land by the Action of Rivers.

MM. Deluc and Dolomieu have most carefully examined the progress of the formation of new ground by means of matters washed down by rivers; and although exceedingly opposed to each other on many points of the Theory of the Earth, they agree in this. These formations augment very rapidly; they must have increased still more rapidly at first, when the mountains furnished more materials to the rivers, and yet their extent is still inconsiderable.

Dolomieu’s Memoir respecting Egypt[90] tends to prove, that the tongue of land on which Alexander caused his city to be built, did not exist in the days of Homer; that they were then able to navigate directly from the island of Pharos into the gulf afterwards called Lake Mareotis; and that this gulf was then, as indicated by Menelaus, from fifteen to twenty leagues in length. It had, therefore, only required the nine hundred years that elapsed between the time of Homer and that of Strabo, to bring things to the state in which this latter author describes them, and to reduce the gulf in question to the form of a lake, of six leagues in length. It is more certain, that, since that time, things have changed still more. The sand thrown up by the sea and winds have formed, between the island of Pharos and the site of ancient Alexandria, a tongue of land two hundred fathoms in breadth, upon which the modern city has been built. It has blocked up the nearest mouth of the Nile, and reduced the lake Mareotis to almost nothing; while, during the same period, the alluvial matter carried down by the Nile, has been deposited along the rest of the shore, and has greatly increased its extent.

The ancients were not ignorant of these changes. Herodotus says, that the Egyptian priests regarded their country as a gift of the Nile. It is only in a manner, he adds, within a short period, that the Delta has appeared[91]. Aristotle observes, that Homer speaks of Thebes as if it had been the only great city in Egypt; and nowhere makes mention of Memphis[92]. The Canopian and Pelusian mouths of the Nile were formerly the principal ones; and the coast extended in a straight line from the one to the other; and in this manner it still appears in the charts of Ptolemy. Since then, the water has been directed into the Bolbitian and Phatnitic mouths; and it is at these entrances into the sea that the greatest depositions have been formed, which have given the coast a semicircular outline. The cities of Rosetta and Damieta, which were built upon these mouths, close to the edge of the sea, less than a thousand years ago, are now two leagues distant from it. According to Demaillet[93], it would only have required twenty-six years to form a promontory of half a league in extent before Rosetta.