GEOLOGY AND MINERALOGY. 
Moloacan, east of tlie Uspanapa River, and a few miles south 
of Xshuatlan. Lamellar specular iron-ore has been found in the 
neighborhood of Tarifa. The ores in the first two localities are 
red haematite, both earthy and compact. There are, besides, in 
many places, deposits of ochre and umber, arising from the 
decomposition of the ferruginous shales. Almost all the por- 
phyries, shales, and sandstones are impregnated with oxide of 
iron, which gives the red and blue tints to the sands and stiff clays 
carried down by the rivers. To the east of the Coatzacoalcos, 
in the vicinity of Ishuatlan and Moloacan, the clay iron-stone 
is magnetic to a marked degree. Magnetic oxide of iron occurs 
at San Jose. 
The hills of San Martin, on the Gulf towards the west, are of 
a volcanic character, and contain cinnabar ore in abundance. 
From this mineral (the sulphuret of mercury) almost all the 
quicksilver of commerce is made. Its location here is a future 
source of riches to the Isthmus. 
The district on the northern slope east of the Coatzacoalcos has 
a geology somewhat different from, and of a more recent charac- 
ter than that on the west. Between that river and the Coachapa 
the land is level, and subject to inundation over a large extent. 
The low hills, which here and there vary the surface, are the 
limestone strata, upheaved similarly to that on the Isla de Taca- 
michapa. Limestone constitutes a range of hills between the lat- 
ter river and the Uspanapa. North of this river, between it and 
Ishuatlan, is a range of hills chiefly of shale, with red haematite. 
About six miles easterly of this is situated a salt and sul- 
phur spring. In this vicinity there exists also a petroleum 
spring, arising from the decomposition of the vegetable matter 
existing in these shales. The quantity which pours out is very 
considerable, and, from its purity, would be a valuable article to 
collect. It hardens very readily into asphalte, small detrital 
pieces of which are picked up in the Uspanapa, and about the 
west base of the Cerro Acalapa. Near Moloacan lignite is met 
with, and corundum at San Jose. 
Obsidian, pitchstone, • and volcanic glass are met with con- 
stantly in beds of streams and in alluvium, washed from the 
Sierra on either side. These have not been seen in place over 
