. Still, we make such fine progress, all hands are in
good cheer, but not a moment of daylight is lost.

_August 25._ We make twelve miles this morning, when we come to
monuments of lava, standing in the river; low rocks mostly, but some of
them shafts more than a hundred feet high. Going on down, three or four
miles, we find them increasing in number. Great quantities of cooled
lava and many cinder cones are seen on either side; and then we come to
an abrupt cataract. Just over the fall, on the right wall, a cinder
cone, or extinct volcano, with a well-defined crater, stands on the very
brink of the canon. This, doubtless, is the one we saw two or three
days ago. From this volcano vast floods of lava have been poured into
the river, and a stream of the molten rock has run up the canon, three
or four miles, and down, we know not how far. Just where it poured over
the canon wall is the fall. The whole north side, as far as we can see,
is lined with the black basalt, and high up on the opposite wall are
patches of the same material, resting on the benches, and filling old
alcoves and caves, giving to the wall a spotted appearance.

The rocks are broken in two, along a line which here crosses the river,
and the beds, which we have seen coming down the canon for the last
thirty miles, have dropped eight hundred feet, on the lower side of the
line, forming what geologists call a fault. The volcanic cone stands
directly over the fissure thus formed. On the side of the river
opposite, mammoth springs burst out of this crevice, one or two hundred
feet above the river, pouring in a stream quite equal in volume to the
Colorado Chiquito.

This stream seems to be loaded with carbonate of lime, and the water,
evaporating, leaves an incrustation on the rocks; and this process has
been continued for a long time, for extensive deposits are noticed, in
which are basins, with bubbling springs. The water is salty.

We have to make a portage here, which is completed in about three hours,
and on we go.

We have no difficulty as we float along, and I am able to observe the
wonderful phenomena connected with this flood of lava. The canon was
doubtless filled to a height of twelve or fifteen hundred feet, perhaps
by more than one flood. This would dam the water back; and in cutting
through this great lava bed, a new channel has been formed, sometimes on
one side, sometimes on the other. The cooled lava, being of firmer
texture than the ro