154 
GEOLOGY AND MINERALOGY. 
latengo, and thence in a southeasterly direction, are a range of 
porphyritic hills with metamorphic sandstones, claystone, and 
jasper, extending as far as the Arroyo de los Otates, where it 
fails into the Chihihua ; these have the same dip, and look with 
their bluff faces in the usual northerly direction. In the passes 
between these hills run the rivers which follow the general slope 
of the sandstone. In that portion of the range west of the Ma- 
latengo river, and near San Juan Guichicovi, iron ore abounds. 
Between these hills and the Malatengo River, after it has taken 
its easterly course, the compact limestone, described previously, 
crops out upon the surface in several places along the line of 
survey. 
Between the Malatengo and the Sarabia, and between the 
latter and the Jaltepec, the surface is less disturbed : granular 
quartz, or quartz-breccia, sandstone, and porphyrinic greenstone 
and sandstone are the underlying rocks. None of these up- 
heavals reach the height of the hills more to the south. While 
the direction of the elevating force was the same, its intensity 
was less. The real inequality of the surface is diminished by 
the accumulation of quartzose gravel and gravelly clay, which 
here occupy the whole surface of the level ground. Five miles 
south of the Jaltepec the compact limestone appears as the sur- 
face rock. Here it overlays coarse conglomerate, consisting of 
hornstone united by a calcareous cement. The limestone forms 
the crest of an elevated ridge dividing the waters of the Jalte- 
pec and Jumuapa. It has a porous structure, but is rather 
hard. It is covered by a mass of weathered fragments, which, 
when removed, show the rock to have a dip of a very small 
angle to the north. The strata are nearly horizontal. 
North of the Naranjo River about seven miles, a range of 
hills 800 feet high, chiefly composed of sandstone conglomerate 
with a calcareous cement, approaches the river Coatzacoalcos 
from the west. The dip is southward, with a more easterly 
strike than the other formations. Above Suchil this conglom- 
erate is met with, the strata dipping at almost every angle. 
On the eastern side of the Island of Tacamichapa the compact 
limestone crops out on the river's edge and forms bold cliffs : 
here it forms the bed of the stream, and rises up east of the river 
