o lower of which have followed in immediate succession, and are
conformable with one another, while the third rests unconformably upon
them, following all the inequalities of the greatly denudated surface
presented by the second formation. Notwithstanding this seeming
interruption in the sequence of these deposits, the third, as we shall
presently see, belongs to the same series, and was accumulated in the
same basin. The lowest set of beds of the whole series is rarely
visible, but it seems everywhere to consist of sandstone, or even of
loose sands well stratified, the coarser materials lying invariably
below, and the finer above. Upon this lower set of beds rests everywhere
an extensive deposit of fine laminated clays, varying in thickness, but
frequently dividing into layers as thin as a sheet of paper. In some
localities they exhibit in patches an extraordinary variety of beautiful
colors,--pink, orange, crimson, yellow, gray, blue, and also black and
white. The Indians are very skilful in preparing paints from these
colored clays, with which they ornament their pottery, and the bowls of
various shapes and sizes made from the fruit of the Cuieira-tree. These
clay deposits assume occasionally a peculiar appearance, and one which
might mislead the observer as to their true nature. When their surface
has been long exposed to the action of the atmosphere and to the heat of
the burning sun, they look so much like clay slates of the oldest
geological epochs, that, at first sight, I took them for primary slates,
my attention being attracted to them by a regular cleavage as distinct
as that of the most ancient clay slates. And yet at Tonantins, on the
banks of the Solimoens, in a locality where their exposed surfaces had
this primordial appearance, I found in these very beds a considerable
amount of well-preserved leaves, the character of which proves their
recent origin. These leaves do not even indicate as ancient a period as
the Tertiaries, but resemble so closely the vegetation of to-day, that I
have no doubt, when examined by competent authority, they will be
identified with living plants. The presence of such an extensive clay
formation, stretching over a surface of more than three thousand miles
in length and about seven hundred in breadth, is not easily explained
under any ordinary circumstances. The fact that it is so thoroughly
laminated shows that, in the basin in which it was formed, the waters
must have been unus