s. Under that lay a thin layer of lava,
then again yet another layer of grey ashes, then lava again. This would
indicate that those boulders had gradually reached their present shape
partly in revolutions through the air thick with cinders, partly by
rolling down or along intermittent stretches of molten lava and cinders
during a great eruption, or perhaps during several successive eruptions.
Personally, I think that it was during various periods of one eruption
before the lava had cooled, so that in its sticky state it would easily
collect the ashes round it, which it would certainly not do in its
polished, solidified state.

When we had passed beyond the western end of the two parallel ranges a
great change was noticeable in the appearance of the country we were
crossing. We missed the long, sweeping, uninterrupted lines of the
scenery, and had before our eyes a confused surface of bosses, mounds and
short undulations, with thick luxuriant vegetation upon them which
prevented my studying carefully their geological formation. The soil, of
a rich red colour, showed every indication of being extremely fertile in
that particular climate.

From the point where we stood, one could well judge the effects of the
great volcanic explosion on the back of the range--the one to our
left--where a long line of buttresses had formed, as if on that side a
subsidence on a large scale had also taken place. It was in any case
curious to notice that at the two termini east and west of the two
parallel ranges white rock in columnar form was exposed in both ranges in
corresponding sites.

The slope noticeable on the north side of the southern range could be
explained by the tilting of the strata where the separation took place.
The angle of the strata clearly demonstrated this fact.

Millions of mosquitoes and _piums_, _carrapatinhos_ and _carrapatos_ made
life unbearable both during the day and night. We never had a moment's
respite. The gnats, too, in thick swarms around us were a constant
worry--we were all day busy removing them from our eyes and ears. They
stung us all over most mercilessly. I was making a botanical collection,
which not only contained specimens of the leaves of all the trees we met
with, but also of minor plants and various kinds of grass. This involved
getting off my mule many times a day. Whenever I put my feet on the
ground or touched a blade of grass I well knew what was in store for me.
At once I became liter