along the surface, must have been far greater than any system of rivers now indicates. That question must be reserved, though we must seek the explanation ol many appearances in this state of things ; not, as they have been commonly sought, in those actions of rivers which we now witness and to which I must at present limit myself. The waters, thus draining along the declivities, hastened to the lowest levels, by the channels which the irregular elevations of the rocky surface must have produced ; uniting into main trunks, and leaving lakes in their courses, as they do at this day. It is true, that the rivers of our own days are not those of antient times ; yet whatever may he their actual direction, their general course was determined by the positions, alti tudes and inclinations of the elevated strata. II the present chains of mountains have been lowered, and their forms rendered more complicated by the enlarge ment and multiplication of their vallies, they still oc cupy the same places ; while, with the nature of the rocks and the inclinations of the strata for our guides, we can safely infer that the general division of the waters over a given country is the same now as it was from the beginning. Near their sources however, they probably still correspond exactly ; the present ravine being an enlargement of the original fissure, as the mountain valley occupies the depression which first tempted the waters to seek the present passage. If, even in these higher elevations, the courses have some times been changed, in consequence of the waste of the rocks, the general conclusion remains. It is in the lower grounds that the great changes have occurred ; since it is in these that they have either essentially mo dified, or even made their channels; ever changing them also, and unavoidably so, when they deposit the very land through which they must construct a passage. Thus, partly modified and partly made, the present