Upon this follow beds of sand and sandstone, varying in the regularity of their strata, reddish in color, often highly ferruginous, and more or less nodulous or porous. They present frequent traces of cross-stratification, alternating with regularly stratified horizontal beds, with here and there an intervening layer of clay. It would seem as if the character of the water basin had now changed, and as if the waters under which this second formation was deposited had vibrated between storm and calm,--had sometimes flowed more gently, and again had been tossed to and fro,--giving to some of the beds the aspect of true torrential deposits. Indeed, these sandstone formations present a great variety of aspects. Sometimes they are very regularly laminated, or assume even the appearance of the hardest quartzite. This is usually the case with the uppermost beds. In other localities, and more especially in the lowermost beds, the whole mass is honeycombed, as if drilled by worms or boring shells, the hard parts enclosing softer sands or clays. Occasionally the ferruginous materials prevail to such an extent, that some of these beds might be mistaken for bog ore, while others contain a large amount of clay, more regularly stratified, and alternating with strata of sandstone, thus recalling the most characteristic forms of the Old Red or Triassic formations. This resemblance has, no doubt, led to the identification of the Amazonian deposits with the more ancient formations of Europe. At Monte Alegre, of which I shall presently speak more in detail, such a clay bed divides the lower from the upper sandstone. The thickness of these sandstones is extremely variable. In the basin of the Amazons proper, they hardly rise anywhere above the level of high water during the rainy season, while at low water, in the summer months, they maybe seen everywhere along the river-banks. It will be seen, however, that the limit between high and low water gives no true measure of the original thickness of the whole series.