ORGAN MOUNTAINS. 493 
account of this singular formation, the glacial phenomena 
which abound in the Organ Mountains are of a peculiar 
character. At first, I was at a loss to explain how loose 
masses of rock, descending from the heights above, should 
be caught on the edges of these basins, instead of rolling 
to the bottom. But their position becomes quite natural 
when we remember that the ice must have remained in 
these depressions long after it had disappeared, or nearly 
disappeared, from the slopes above. Hindered from ad- 
vancing, these huge masses of rock have become gradually 
embedded in the soil, and are now solidly fixed in positions 
which would be perfectly inexplicable, unless we suppose 
the basin to have been formerly filled with something which 
offered an obstacle to their farther descent. Moraines also 
abut upon these depressions, coming to an abrupt close 
upon their margin. Morainic soil that is, masses of drift 
with all sorts of loose materials buried in it - - abounds 
everywhere in this region ; but, on the whole, the glacial 
phenomena are difficult to study, because the heavy growth 
of forest has covered all inequalities of the soil, and, except 
where sections have been made or ground has been cleared, 
the outlines are lost." 
This was our final excursion in Brazil. The next morn 
ing we returned to the city ; and the few remaining days 
were spent in preparations for departure, and in bidding 
farewell to the friends who had made Rio de Janeiro almost 
like a home to us. Among the pleasant incidents of this 
last week, was a breakfast given by Mr. Ledgerwood, who 
was then conducting the business of the American legation 
in the temporary absence of our Minister, General Webb. 
This occasion, at which Mr. Agassiz was invited to meet 
several members of the Brazilian administration, gave him 
