The extreme rapidity of our railroad journeys is very mischievous even to the strong;--in many cases fatal to the ailing. To pass, as so many do, from Paris to the Mediterranean in twenty-four hours, passing at every hour into a different climate, is as perilous a thing as a nervous person can do. You arrive agitated, giddy. When Madame de Sevigné took a whole month to travel from Brittany to Provence, she proceeded by slow and calculated degrees from one climate to another, and its opposite. She proceeded, by slow degrees, from the maritime climate of the West into the inland climate of Burgundy. Then, travelling slowly by the upper Rhone into Dauphiny, she, with the greater safety and comfort, braved the free winds of Valence and of Avignon; then, halting awhile, and resting at Aix, in the interior of Provence, far from the Rhone and from its shores, she made herself Provençal in lungs. France has the enviable advantage of being between two seas, and thence the facility of alternating, as the disease may require, between the saline tonicity of the Mediterranean and the moister and--except in case of tempest--the far milder air of the Ocean. On each of the two coasts there is a graduated scale of stations, more or less mild, more or less strengthening. It is very interesting to observe, and very useful to follow, this double scale,--proceeding, as a general thing, from weaker to stronger. The climate of the Ocean parting from the strong, rough, ever-heaving waters of the channel, becomes extremely mild at the South of Brittany, milder still in the Gironde, and mildest of all in the land-locked basin of Arcachon. The air of the Mediterranean, which we may call circular, has its highest note in the dry, though keen, climate of Provence and Genoa, becomes more mild as you approach Pisa, milder and less variable in Sicily, and at Algiers attains a wonderful mildness and regularity. And on your return be sure of a balmy air at Majorca and the little ports of the Rousillon, so well sheltered from the harsh north wind. The Mediterranean commands our admiration by two characteristics; the beauty of its shores and the brilliant purity of its sky and atmosphere. Very salt, very bitter is that sea; but what a glorious blue sky is above it! It gives out by evaporation about thrice as much water as it receives from all its tributary rivers. It would become all salt, like that terrible Dead Sea, but for the lower currents, the under-tow, like that from Gibraltar, for instance, were not constantly tempering it with the waters of the Ocean.