The Gallinazo (Cathartes atratus)
has a different range from the last species, as it never occurs
southward of latitude 41 degrees. Azara states that there exists a
tradition that these birds, at the time of the conquest, were not
found near Monte Video, but that they subsequently followed the
inhabitants from more northern districts. At the present day they
are numerous in the valley of the Colorado, which is three hundred
miles due south of Monte Video. It seems probable that this
additional migration has happened since the time of Azara. The
Gallinazo generally prefers a humid climate, or rather the
neighbourhood of fresh water; hence it is extremely abundant in
Brazil and La Plata, while it is never found on the desert and arid
plains of Northern Patagonia, excepting near some stream. These
birds frequent the whole Pampas to the foot of the Cordillera, but
I never saw or heard of one in Chile: in Peru they are preserved as
scavengers. These vultures certainly may be called gregarious, for
they seem to have pleasure in society, and are not solely brought
together by the attraction of a common prey. On a fine day a flock
may often be observed at a great height, each bird wheeling round
and round without closing its wings, in the most graceful
evolutions. This is clearly performed for the mere pleasure of the
exercise, or perhaps is connected with their matrimonial alliances.

I have now mentioned all the carrion-feeders, excepting the condor,
an account of which will be more appropriately introduced when we
visit a country more congenial to its habits than the plains of La
Plata.

In a broad band of sand-hillocks which separate the Laguna del
Potrero from the shores of the Plata, at the distance of a few
miles from Maldonado, I found a group of those vitrified, siliceous
tubes, which are formed by lightning entering loose sand. These
tubes resemble in every particular those from Drigg in Cumberland,
described in the "Geological Transactions." (3/10. "Geological
Transactions" volume 2 page 528. In the "Philosophical
Transactions" 1790 page 294, Dr. Priestley has described some
imperfect siliceous tubes and a melted pebble of quartz, found in
digging into the ground, under a tree, where a man had been killed
by lightning.) The sand-hillocks of Maldonado, not being protected
by vegetation, are constantly changing their position. From this
cause the tubes projected above the surface; and numerous fragments
lying near,