Bombam Post-house, in the focus of change from cirrus to
cumulus, and stratus, and storm:

"The winds are very gentle, and curl the cirrus or hairy clouds in
most graceful shapes about the hoary-headed Andes, in rich and
delicate clusters; when the peak is concealed, all but the blue tinge
below the snow, we see a natural bridal vail. An _easterly wind_
lifts and turns them to dark, cumulus clouds, settled on the frosty
crown, like an old man's winter cap; the physiognomical expression is
that of anger. The change is accompanied by thunder, and seems to
command all around to clothe themselves for storms. The cold rain
comes down in _fine drops_ upon us; the day grows darker, and the
_clouds press close upon the earth_."

During an excursion east of Cuzco--

"Turning from the river, we ascend a steep ridge of mountains--the
eastern range at last. A heavy mist _wafts upward as the winds drive
it against the side of the Andes_, so that our view is shortened to a
few hundred yards. We hope the curtain will rise that we may view the
productions of the tropical valley below; but the mist thickens, and
the day gets dark with heavy, heaped-up black clouds; a rain-storm
follows. The grasses are thrifty, and the top of the ridge covered
with a thick sod. By barometer, we stand eleven thousand one hundred
feet above the level of the sea."

In May following, having spent the rainy season in Cochabamba, he travels
north--

"Our route from Tarma to Oruro was south. We traveled ahead of the
sun. In December, when we arrived in Cochabamba, the sun had just
passed us. As soon as he did so, the rains descended heavily on this
side of the ridge; it was impossible to proceed. The roads were
flooded, the ravines impassable, and the arrieros put off their
journey until the dry season had commenced. After the sun passed the
zenith of Cochabamba, and had fairly moved the rain belt after him
toward the north, then we came out from under shelter, and are now
walking behind the rain belt in dry weather, while the inhabitants
are actively employed in tending their crops."

So on the north of the equatorial belt, along the whole line of the Andes,
up to the northern boundary of the desert valley of the Gila, rain falls
on the high mountain-ranges, owing to the contiguity of the counter-trade
and the