Chapter XVII.
Journey Over the Pass and by Lago Maorno.
As we had ascended, the soft, ill-bedded limestone of the lower roots of the hills, had gradually given way to indurated liassic-looking hard, elastic, cherty beds of yellow limestone, in distinct and highly-inclined layers, probably metamorphic (see Section)—these, after many alternations came back to the same soft, cretaceous-looking stuff, and are finally lost, (as we top the steep and get upon the more level table of the shoulder and elevated valley), under a deep loose deposit of almost perfectly pure and fine white sand, (from which the pass and town derive their name), mixed largely, but unequally, with impalpable chalky particles. This extends to beyond Tardiano, under the southern summit of Monte Vajana; but at various points the rock beneath might be seen, and proved that we had lost the limestone proper, and got upon an endless succession of thin beds, all more or less metamorphic, consisting of ash-yellow limestone, often highly quartzose, hard and elastic, alternating with thick and thin beds, of grey and purple and green clays, and of variegated marls; and in one place some beds of 4 to 6 feet of impure alabaster, all highly inclined. (Geolog. section, Diagram No. 241.)
At the highest point of the pass, near Arena Bianca,
