ENGINEERING EEPOBTS. 
27 
the surface. This would reduce the summit at grade to only 
,60 feet above the plains of Chivela, and 793 feet above the 
Pacific. 
From the surface indications, there is reason to believe that the 
material in this cut will be found almost entirely composed of 
talcose and clay slates — rocks which generally disintegrate on 
exposure to the atmosphere, and are very easily blasted in their 
more solid state. It is very probable that from five to twenty 
feet of the surface can be readily removed with the pick and 
shovel — the remainder by blasting. 
Descending from the summit on a sixty-feet grade, the gen- 
eral course of the line is nearly south, and continues on the 
right of the valley of the Summit Arroyo, till it reaches Danta 
Pass, where the valley opens between the ends of two high 
mountains into that of the " Torrente de Masahua" The 
mountain on the right is called " Masahuita /" that on the left, 
" Cerro de Espinosa" 
From the summit to Masahuita, we encounter a succession of 
ridges or sharp spurs of the main range. These will be difficult 
to turn without heavy cutting and filling, or making four or 
five short tunnels ; which last, for the sake of alignment and 
want of more extended surveys, I have estimated upon, although 
they may, in all probability, be avoided, by throwing the line a 
little further to the east. These tunnels occur about a mile be- 
low the summit, and in the aggregate will be nearly half a mile 
long, contiguous to each other, and separated only by steep inter- 
vening ravines, which serve as natural shafts. A very favorable 
feature about these tunnels is, that they will admit of being 
worked at not less than ten different points at the same time, and 
without the necessity of raising any of the material. 
There is but little choice of ground across the spurs ; for, by 
throwing the line to the right, we at once encounter the main 
ridge, which is too high, and by laying it to the left, it as sud- 
denly drops into the valley, the bottom of which is nearly 150 
feet below the grade line. 
The material on the line, from the summit to Masahua, is 
mostly composed, like that of the summit itself, of talcose and 
clay slates, with the exception that they partake more of a shaly 
