125. Had we come in the month of April or May, we should have found the glacier below the ice-fall also covered with snow, which is now entirely cleared away by the heat of summer. Nay, more, the ice there is obviously melting, forming running brooks which cut channels in the ice, and expand here and there into small blue-green lakes. Hence you conclude with certainty that below the ice-fall _the quantity of frozen material falling upon the glacier is less than the quantity melted_. 126. And this forces upon us another conclusion: between the glacier below the ice-fall and the plateau above it there must exist a line where the quantity of snow which falls _is exactly equal_ to the quantity annually melted. This is the _snow-line_. On some glaciers it is quite distinct, and it would be distinct here were the ice less broken and confused than it actually is. 127. The French term _névé_ is applied to the glacial region above the snow-line, while the word _glacier_ is restricted to the ice below it. Thus the snows of the Col du Géant constitute the névé of the Glacier du Géant, and in part, the névé of the Mer de Glace. 128. But if every year thus leaves a residue of snow upon the plateau of the Col du Géant, it necessarily follows that the plateau must get annually higher, _provided the snow remain upon it_. Equally certain is the conclusion that the whole length of the glacier below the cascade must sink gradually lower, _if the waste of annual melting be not made good_. Supposing two feet of snow a year to remain upon the Col, this would raise it to a height far surpassing that of Mont Blanc in five thousand years. Such accumulation must take place if the snow remain upon the Col; but the accumulation does _not_ take place, hence the snow does not remain on the Col. The question then is, whither does it go? [Illustration: SKETCH-PLAN, SHOWING THE MORAINES, _a_, _b_, _c_, _d_, _e_, OF THE MER DE GLACE.] § 16. _Branches and Medial Moraines of the Mer de Glace from the Cleft Station._ 129. We shall grapple with this question immediately. Meanwhile look at that ice-valley in front of us, stretching up between Mont Tacul and the Aiguille de Léchaud, to the base of the great ridge called the Grande Jorasse. This is called the Glacier de Léchaud. It receives at its head the snows of the Jorasse and of Mont Mallet, and joins the Glacier du Géant at the promontory of the Tacul. The glaciers seem welded together where they join, but they continue distinct. Between them you clearly trace a stripe of débris (_c_ on the annexed sketch-plan); you trace a similar though smaller stripe (_a_ on the sketch), from the junction of the Glacier du Géant with the Glacier des Périades at the foot of the Aiguille Noire, which you also follow along the Mer de Glace.