Sec. 6. The reader is, no doubt, already aware that the chain of the Mont Blanc is bordered by two great valleys, running parallel to each other, and seemingly excavated on purpose that travellers might be able to pass, foot by foot, along each side of the Mont Blanc and its aiguilles, and thus examine every peak in succession. One of these valleys is that of Chamouni, the other that of which one half is called the Allee Blanche, and the other the Val Ferret, the town of Cormayeur being near its centre, where it opens to the Val d'Aosta. Now, cutting the chain of Mont Blanc right across, from valley to valley, through the double range of aiguilles, the section would be[59] as Fig. 29 here, in which _a_ is the valley of Chamouni, _b_ the range of aiguilles of Chamouni, _c_ the range of the Geant, _d_ the valley of Cormayeur. [Illustration: 30. The Aiguille Charmoz.] Ideal. Actual. The little projection under M is intended to mark approximately the position of the so well-known "Montanvert." It is a great weakness, not to say worse than weakness, on the part of travellers, to extol always chiefly what they think fewest people have seen or can see. I have climbed much, and wandered much, in the heart of the high Alps, but I have never yet seen anything which equalled the view from the cabin of the Montanvert; and as the spot is visited every year by increasing numbers of tourists, I have thought it best to take the mountains which surround it for the principal subjects of our inquiry. Sec. 7. The little eminence left under M truly marks the height of the Montanvert on the flanks of the Aiguilles, but not accurately its position, which is somewhat behind the mass of mountain supposed to be cut through by the section. But the top of the Montanvert is actually formed, as shown at M, by the crests of the oblique beds of slaty crystallines. Every traveller must remember the steep and smooth beds of rock like sloping walls, down which, and over the ledges of which, the path descends from the cabin to the edge of the glacier. These sloping walls are formed by the inner sides of the crystalline beds,[60] as exposed in the notch behind the letter M.