414 A JOURNEY IN BRAZIL. 
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 char- 
acter 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 regu- 
larly laminated, or assume even the appearance of the hard- 
est quartzite. This is usually the case with the uppermost 
beds. In other localities, and more especially in the lower- 
most 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 may 
be observed 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. 
