Before we speak of individual mountains and their shapes, it is important to bear in mind another fact about mountain-chains; namely, that they are very low in proportion to their breadth and length. The great heights reached by some mountains produce such a powerful impression on our senses that we hardly realise how very insignificant they really are. It is only by drawing them on a true scale that we can realise this. The surface of the earth is so vast that even the highest mountains are in proportion but as the little roughnesses on the skin of an orange. Fig. 2 (see chap, vii., p. 236) represents a section through the Highlands, drawn on the same scale for height as for length. What has been said about the Highland plateau applies equally well to many other mountain-ranges. Mr. Ruskin observed something rather similar in the Alps. He says,-- "The longer I stayed in the Alps, and the more closely I examined them, the more I was struck by the one broad fact of there being a vast Alpine plateau, or mass of elevated land, upon which nearly all the highest peaks stood like children set upon a table, removed, in most cases, far back from the edge of the plateau, as if for fear of their falling; ... and for the most part the great peaks are not allowed to come to the edge of it, but remain like the keeps of castles, withdrawn, surrounded league beyond league by comparatively level fields of mountains, over which the lapping sheets of glaciers writhe and flow, foaming about the feet of the dark central crests like the surf of an enormous sea-breaker hurled over a rounded rock and islanding some fragment of it in the midst. And the result of this arrangement is a kind of division of the whole of Switzerland into an upper and a lower mountain world,--the lower world consisting of rich valleys, bordered by steep but easily accessible, wooded banks of mountain, more or less divided by ravines, through which glimpses are caught of the higher Alps; the upper world, reached after the first steep banks of three thousand or four thousand feet in height have been surmounted, consisting of comparatively level but most desolate tracts of moor and rock, half covered by glacier, and stretching to the feet of the true pinnacles of the chain." He then points out the wisdom of this arrangement, and shows how it protects the inhabitants from falling blocks and avalanches; and moreover, the masses of snow, if cast down at once into the warmer air, would melt too fast and cause furious inundations.