s possible that the lava cooled faster on the sides
against the walls and that the center ran out; but of this we can only
conjecture. There are other places where almost the whole of the lava is
gone, only patches of it being seen, where it has caught on the walls.
As we float down we can see that it ran out into side canyons. In some
places this basalt has a fine, columnar structure, often in concentric
prisms, and masses of these concentric columns have coalesced. In some
places, when the flow occurred the canyon was probably about the same
depth that it is now, for we can see where the basalt has rolled out on
the sands, and--what seems curious to me--the sands are not melted or
metamorphosed to any appreciable extent. In places the bed of the river
is of sandstone or limestone, in other places of lava, showing that it
has all been cut out again where the sandstones and limestones appear;
but there is a little yet left where the bed is of lava.

What a conflict of water and fire there must have been here! Just
imagine a river of molten rock running down into a river of melted snow.
What a seething and boiling of the waters; what clouds of steam rolled
into the heavens!

Thirty-five miles to-day. Hurrah!

_August 26.--_The canyon walls are steadily becoming higher as we
advance. They are still bold and nearly vertical up to the terrace. We
still see evidence of the eruption discovered yesterday, but the
thickness of the basalt is decreasing as we go down stream; yet it has
been reinforced at points by streams that have come down from volcanoes
standing on the terrace above, but which we cannot see from the river
below.

Since we left the Colorado Chiquito we have seen no evidences that the
tribe of Indians inhabiting the plateaus on either side ever come down
to the river; but about eleven o'clock to-day we discover an Indian
garden at the foot of the wall on the right, just where a little stream
with a narrow flood plain comes down through a side canyon. Along the
valley the Indians have planted corn, using for irrigation the water
which bursts out in springs at the foot of the cliff. The corn is
looking quite well, but it is not sufficiently advanced to give us
roasting ears; but there are some nice green squashes. We carry ten or a
dozen of these on board our boats and hurriedly leave, not willing to be
caught in the robbery, yet excusing ourselves by pleading our great
want. We run down a short distance to wh