LAVA. 95 
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 rocks of which the walls are composed, remains in some places; in 
others a narrow channel has been cut, leaving a line of basalt on either side. 
It is possible that the lava cooled faster on the sides against the walls, and 
that the centre ran out ; but of this we can only conjecture. There are 
other places, where almost the whole of the lava is gone, patches of it only 
being seen where it has caught on the walls. As we float down, we can see 
that it ran out into side canons. In some places this basalt has a fine, col 
umnar structure, often in concentric pi isms, and masses of these concentric 
columns have coalesced. In some places, when the flow occurred, the canon 
was probably at about the same depth as 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, show 
ing 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 canon 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 the stream; yet it has been rein 
forced 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 
