152 
GEOLOGY AND MINERALOGY. 
Higher up in the same slopes, compact limestone is met with ; 
and this rock constitutes the highest points of all the hills upon 
this range, as also in the chains above enumerated which lie 
north. Talcose slate with talc rock constitutes the basis rock of 
these mountains, and is that upon which the limestone reposes. 
The dip of these slates and limestones varies, but averages about 
45°, in a direction southwest — the bluff edges of the hills face 
the northeast. It is on this side that the talc rocks are easily 
seen underlying the limestone, nowhere more apparent than 
when passing along the Torrentera and looking south upon the 
northern sides of the Masahua, where abrupt cliffs and nearly 
vertical walls of rock, from 200 to 300 feet high, are occasionally 
met with. 
The elevating force which raised these hills seems to have 
been exerted with more energy upon the Masahuita than upon 
the Masahua range, as the former is the more elevated ; geo- 
logically speaking, they are repetitions of each other and of the 
Hucamaya, their formation (reckoning from above downward) 
consisting of : 
1. Sandstone, grit and inetamorphic. 
2. Limestone, gray and dark-colored. 
3. Talc, in rock and shale. 
Their analogous form and conformation are given in the sec- 
tion, and are well marked in the view of Masahua. The lower 
portions of the talc slate are intermixed with greenstone and hy- 
persthene rock ; and in some places it becomes magnesian, and 
verges into a steatitic rock. Yeins of milk-quartz cut through the 
sandstone, especially upon the flanks of Masahuita and Espinosa. 
South of these hills, and before the Pacific plains are reached 
from the north, there lie several scattered hills about 200 feet 
high, having round rugged summits, with a gradual slope to the 
south. The limestone of these ranges is a very compact, light- 
colored stone, dense, and so altered as to become nearly a crys- 
talline marble ; it effervesces strongly with acids, burns well, 
and is well adapted for building purposes, for stone or mortar. 
This limestone bed presents a semicircular form, commencing 
from the Coatzacoalcos, east of Santa Maria Chimalapa, sweep- 
ing south to San Miguel, west to the rancho del Zapotal, and 
