The top, however, of a heavy bank of clouds, which remained almost constantly in one position, was the most promising sign, and eventually turned out a true harbinger.

At first the clouds were mistaken for the mountains themselves, instead of the masses of vapour condensed by their icy summits.
APRIL 26, 1834.
We this day met with a marked change in the geological structure of the plains.

From the first starting I had carefully examined the gravel in the river, and for the two last days had noticed the presence of a few small pebbles of a very cellular basalt.

These gradually increased in number and in size, but none were as large as a man's head.

This morning, however, pebbles of the same rock, but more compact, suddenly became abundant, and in the course of half an hour we saw, at the distance of five or six miles, the angular edge of a great basaltic platform.