And see how some of the longest of the banners on the highest peaks are streaming perfectly free from peak to peak across intervening notches or passes, while others overlap and partly hide one another.
As to their formation, we find that the main causes of the wondrous beauty and perfection of those we are looking at are the favorable direction and force of the wind, the abundance of snow-dust, and the form of the north sides of the peaks.

In general, the north sides are concave in both their horizontal and vertical sections, having been sculptured into this shape by the residual glaciers that lingered in the protecting northern shadows, while the sun-beaten south sides, having never been subjected to this kind of glaciation, are convex or irregular.

It is essential, therefore, not only that the wind should move with great velocity and steadiness to supply a sufficiently copious and continuous stream of snow-dust, but that it should come from the north.

No perfect banner is ever hung on the Sierra peaks by the south wind.

Had the gale today blown from the south, leaving the other conditions unchanged, only swirling, interfering, cloudy drifts would have been produced; for the snow, instead of being spouted straight up and over the tops of the peaks in condensed currents to be drawn out as streamers, would have been driven over the convex southern slopes from peak to peak like white pearly fog.
It appears, therefore, that shadows in great part determine not only the forms of lofty ice mountains, but also those of the snow banners that the wild winds hang upon them.
Earthquake Storms The avalanche taluses, leaning against the walls at intervals of a mile or two, are among the most striking and interesting of the secondary features of the Valley.