the progress of rivers to the ocean is not so rapid as that of man to error. it is not long since it was discovered that all rivers originate in those eternal masses of snow which cover the summits of lofty mountains, those snows in rain, that rain in the vapor exhaled from the land and sea; and that thus everything is a link in the great chain of nature.
when a boy, i heard theses delivered which proved that all rivers and fountains came from the sea. this was the opinion of all antiquity. these rivers flowed into immense caverns, and thence distributed their waters to all parts of the world.
when aristeus goes to lament the loss of his bees to cyrene his mother, goddess of the little river enipus in thessaly, the river immediately divides itself, forming as it were two mountains of water, right and left, to receive him according to ancient and immemorial usage; after which he has a view of those vast and beautiful grottoes through which flow all the rivers of the earth; the po, which descends from mount viso in piedmont, and traverses italy; the teverone, which comes from the apennines; the phasis, which issues from mount caucasus, and falls into the black sea; and numberless others.
virgil, in this instance, adopted a strange system of natural philosophy, in which certainly none but poets can be indulged.
such, however, was the credit and prevalence of this system that, fifteen hundred years afterwards, tasso completely imitated virgil in his fourteenth canto, while imitating at the same time with far greater felicity ariosto. an old christian magician conducts underground the two knights who are to bring back rinaldo from the arms of armida, as melissa had rescued rogero from the caresses of alcina. this venerable sage makes rinaldo descend into his grotto, from which issue all the rivers which refresh and fertilize our earth. it is a pity that the rivers of america are not among the number. but as the nile, the danube, the seine, the jordan, and the volga have their source in this cavern, that ought to be deemed sufficient. what is still more in conformity to the physics of antiquity is the circumstance of this grotto or cavern being in the very centre of the earth. of course, it is here that maupertuis wanted to take a tour.
after admitting that rivers spring from mountains, and that both of them are essential parts of this great machine, let us beware how we give in to varying and vanishing systems.
when maillet imagined that the sea had formed the mountains, he should have dedicated his book to cyrano de bergerac. when it has been said, also, that the great chains of mountains extend from east to west, and that the greatest number of rivers also flow always to the west, the spirit of system has been more consulted than the truth of nature.
with respect to mountains, disembark at the cape of good hope, you will perceive a chain of mountains from the south as far north as monomotapa. only a few persons have visited that quarter of the world, and travelled under the line in africa. but calpe and abila are completely in the direction of north and south. from gibraltar to the river guadiana, in a course directly northward, there is a continuous range of mountains. new and old castile are covered with them, and the direction of them all is from south to north, like that of all the mountains in america. with respect to the rivers, they flow precisely according to the disposition or direction of the land.
the guadalquivir runs straight to the south from villanueva to san lucar; the guadiana the same, as far as badajos. all the rivers in the gulf of venice, except the po, fall into the sea towards the south. such is the course of the rhone from lyons to its mouth. that of the seine is from the north-northwest. the rhine, from basle, goes straight to the north. the meuse does the same, from its source to the territory overflowed by its waters. the scheldt also does the same.
why, then, should men be so assiduous in deceiving themselves, just for the pleasure of forming systems, and leading astray persons of weak and ignorant minds? what good can possibly arise from inducing a number of people — who must inevitably be soon undeceived — to believe that all rivers and all mountains are in a direction from east to west, or from west to east; that all mountains are covered with oyster-shells — which is most certainly false — that anchors have been found on the summit of the mountains of switzerland; that these mountains have been formed by the currents of the ocean; and that limestone is composed entirely of seashells? what! shall we, at the present day, treat philosophy as the ancients formerly treated history?
to return to streams and rivers. the most important and valuable things that can be done in relation to them is preventing their inundations, and making new rivers — that is, canals — out of those already existing, wherever the undertaking is practicable and beneficial. this is one of the most useful services that can be conferred upon a nation. the canals of egypt were as serviceable as its pyramids were useless.
with regard to the quantity of water conveyed along the beds of rivers, and everything relating to calculation on the subject, read the article on “river,” by m. d’alembert. it is, like everything else done by him, clear, exact, and true; and written in a style adapted to the subject; he does not employ the style of telemachus to discuss subjects of natural philosophy.