It seems therefore reasonable to take the entire curve as forming the Cévennes from the depression of the Jarrêt, through which runs the line from Lyons to the coalfields of S. Etienne, as the northern limit, and the Montagne Noire, east of the gap of Revel, by which the road by which Castelnaudary and Castres are linked, as the western termination. "The Cévennes," says Onésime Reclus, "have this striking feature, that they separate two climates, two vegetations, two natures. To the north and to the west are rain, snow, light fog silvered by the moon, and dense vapours which the sun cannot pierce; and the streams that water the smallest valleys nourish rich green meadows; to the south and east is a blazing sun, are glare, heat, drought, barrenness, dust, the vine, the olive, springs of water few and far between, but where they do issue, copious and clear; here—contrasts of colour, sharp-cut horizons, more beautiful than those of the north. What a contrast within a few leagues' distance between the verdure of Mezamet and the vari-coloured marbles of Cannes, between the Agout and the Salvetat d'Angles ... between the valley of the Dourbie at Nant and the Hérault at Ganges, between the Tarn at Pont-de-Montvert and the embattled gorges of the Gardons, between the Allier at La Bastide and the ravines down which rushes the Cèze, between the young Loire and the terrible rapids of the Ardèche ... on one side a French Siberia, on the other an Africa where the sirocco does not parch up the harvests, but where the mistral shrieks, itself producing a brief winter."[1] The chain of the Cévennes, of which Mézenc may be regarded as the hinge, forms a ridge on the right bank of the Rhône, running for a while parallel to the French Alps upon the left bank. But whereas these latter turn and curve to the east, forming the Maritime Alps, the Cévennes have bent in exactly the opposite direction. Geographically and historically the Cévennes divide into two great sections—the Cévennes Méridionales and the Cévennes Septentrionales. This continuous mountain ridge, in fact, forms a line of separation of waters very distinct, without solution of continuity, and which, in spite of the variety of its geological structure, has been determined by the same fold in the earth's crust, by one and the same act of pressure. From the main chain, like the rib of a fern, extend lateral offshoots, between which are valleys watered by the drainage of the principal spinal chain. On the east side of the Cévennes these are all approximately at right angles to the axis. But this is not the case on the west side; nor is it so on the south. On this latter, before the main range a sort of outwork has been thrown up that deflects the streams, where they have not cut through it. These bastions are the Garrigues and the Espinouse.