miles above Almagres we saw the first bluff upon its shores. It consisted of green slate, and was about 60 feet high. A decided change in the height of the shores became noticeable, and not unfrequently we saw evidences of strong flood-currents.
Five miles above Almagres, the river becomes uninterruptedly tortuous, being filled with extensive bars and snags. Its current flows at the rate of 3 and 4.5 feet per second, in long shallow stretches; 7 miles above Almagres one of these bars had dammed the river so high that it broke through another place, or 'rompido,' in about 1848, running them through the old channel that it had excavated in 1834. This rompido shortened the river-course 6 miles, but the bar now below this point is so shallow that the next flood may again alter its course. From the best information I have been able to obtain, these breaks take place every twelve or fifteen years. Our travel through this part of the river was very unpleasant, as it rained in torrents, and the current was so swift that the canoes passed the steam-launch with ease, though the latter carried 70 pounds of steam. The launch became disabled and was sent back, though she could not, in any case, have proceeded much farther up stream, on account of the frequent bars, over which our canoes now often found difficult crossings.
At Peña Blanca we saw the first indication of stratified rocks thus far noticed; the banks were 60 feet high, composed of white and green strata of clay, with a shallow synclinal. The average strike was about 12°, and dipping south. The natives use this clay in the manufacture of their rude pottery.
The river bottom is here hard, and is made up of sharp sand, small gravel, and clay.
From the island of Guapinoloya to Pedernal Island, the river is very deep, with a clean clay bottom, and only occasionally sandy.
The temperature of this river is about 3 degrees cooler than the air in the morning, and 4 degrees cooler at noon. This was only observed during our journey of eight days up the river.
After passing the Chalchijalpa River, the banks are quite high, and the Coatzacoalcos grows wider and shallow opposite the island of Oaxaqueña, where it is about 1,400 feet wide, with 12 feet of water in the channel, which is about 200 feet wide. The river branch on the north-west side of this island was nearly dry. In latitude 17° 27' north, there is a dangerous bend, with a high bluff in the receiving shore, and a large sand deposit on the salient shore. Farther up we passed the Perla and Platanal Islands, covered with camalote, gimba, and crocodiles. The camalote is a tall grass eaten by cattle; the gimba is a species of bamboo.
The roots of both plants afford a most effective protection to the banks against the heaviest floods.
Opposite these islands the bottom is clean, plastic clay, which occasioned great difficulty to the pole-men, whose poles were buried fast.
In latitude 17° 23' north, longitude 94° 25' west of Greenwich, the country becomes wild and wooded; the current is swifter, and the river narrow-, although the volume of water appears undiminished, even after passing above the Chalchijalpa.
The Chalchijalpa is a large river, whose different sources come from the
