rom Vera Cruz
we came upon sandstone immediately after leaving the sandy plains; and
a few miles further on we reached the limestone, very much as it is
represented in Burkart's profile of the country from Tampico upwards
towards San Luis Potosi. The mountain-plateaus, such as the plains of
Mexico and Puebla, are hollows filled up and floored with horizontal
strata of tertiary deposits, which again are covered by the constantly
accumulating layers of alluvium.

Our heavy pull up the mountain-side has brought us into a new scene.
Every one knows how the snow lies in the valleys of the Alps, forming a
plain which slopes gradually downward towards the outlet Imagine such a
valley ten miles across, with just such a sloping plain, not of snow
but of earth. There has been no rain for months, and the surface of the
ground is parched and cracked all over. There is hardly a tree to be
seen except clumps of wood on the mountain-sides miles off,--no
vegetation but tufts of coarse grass, among which herds of
disconsolate-looking cattle are roaming; the vaqueros, (herdsmen) are
cantering about after them on their lean horses, with their lazos
hanging in coils on their left arms, and now and then calling to order
some refractory beast who tries to get away from the herd, by sending
the loop over his horns or letting it fall before him as he runs, and
hitching it up with a jerk round his hind legs as he steps within it.
But the poor creatures are too thirsty and dispirited just now to give
any sport, and the first touch of the cord is enough to bring them back
to their allegiance.

From the decomposed porphyry of the mountains carbonate of soda comes
down in solution to the valleys. Much of this is converted into natron
by the organic matter in the soil, and forms a white crust on the
earth. More of the carbonate of soda, mixed in various proportions with
common salt, drains continually out in the streams, or filters into the
ground and crystallizes there. This is why there is not a field to be
seen, and the land is fit for nothing but pasture. But when the rains
come on in a few months, say our friends in the diligence, this dismal
waste will be a luxuriant prairie, and the cattle will be here by
thousands, for most of them are dispersed now in the lower regions of
the tierra templada where grass and water are to be had.

My companion and I climb upon the top of the diligence to spy out the
land. The grand volcano of Orizaba had b