soil is of marvelous fertility, even for
Brazil; the endless rivers and labyrinths of channels teem with fish and
turtle; a fleet of steamers might anchor at any season of the year in
the lake, which has uninterrupted water communication straight to the
Atlantic. What a future is in store for the sleepy little tropical
village!" Here Bates pursued butterflies for four years and a half, and
Agassiz fished for six months.

[Footnote 137: Smyth says the town gets its name from the clearness of
the water; but Herndon found it muddy, and, to our eyes, it was dark as
the Negro.]

[Illustration: Natives on the Middle Amazon.]

Ega is the half-way point across the continent, but its exact altitude
above the sea is unknown. Herndon's boiling apparatus gave two thousand
feet, and, what is worse, the lieutenant believed it. Our barometer made
it one hundred feet; but as our instrument, though perfect in itself,
behaved _very_ strangely on the Middle Amazon, we do not rely on the
calculation. The true height is not far from one hundred and twenty-five
feet, or one fifth the elevation of the middle point in the North
American continent.[138] Taking on board salt fish, turtle-oil, and
tiles, we left Ega two hours after midnight, reaching Coary at noon.
The Amazon began to look more like a lake than a river, having a width
of four or five miles. Floating gulls and rolling porpoises remind one
of the sea. Coary is a huddle of fifteen houses, six of them plastered
without, whitewashed, and tiled. It is situated on a lake of the same
name--the expanded outlet of a small river whose waters are dark brown,
and whose banks are low and covered with bushes. Here we took in turtles
and turtle-oil, Brazil nuts and cocoa-nuts, rubber, salt fish, and wood;
and, six hours after leaving, more fish and rubber were received at
Cudaja. Cudaja is a lonely spot on the edge of an extensive system of
back-waters and lakes, running through a dense unexplored forest
inhabited by Mura savages.

[Footnote 138: For a discussion of the barometric perturbations on the
Amazon, see _American Journal of Science_ for Sept., 1868.]

At three in the afternoon of Christmas, seventy-four hours' running time
from Tabatinga, we entered the Rio Negro. Strong is the contrast between
its black-dyed waters and the yellow Amazon. The line separating the two
rivers is sharply drawn, the waters meeting, not mingling. Circular
patches of the dark waters of the Negro are see