82 ROUTE NEAR THE THIRTY-SECOND PARALLEL. 
may be constructed with easy grades. The instrumental profile, however, shows that what to 
the eye appears to be a plain, is really an undulating surface, constantly rising and falling, rarely 
horizontal, and that the plain is converted into a series of basins, the steepest parts of which are 
found in passing around the lost 1n0untains, or through the passes in them. The summits of these 
basin-rims or passes are generally about 400 teet above the lowest parts of the basins, though 
in two instances 850 and 1,200 feet respectively; the mean elevation of the basins above the 
level of the sea being about 4,100 feet, decreasing from near the Rio Grande, where it is 4,350 
feet, towards the Gila. The mean elevation of the lowest points of the dividing rims is 4,700 
feet, the highest of them, the pass through the Chiricahui range, being 5,180 feet. Seven basins 
are crossed, the eighth continuing or conducting to the Gila. Except through the mountain 
passes, the surface is so smooth as to require but little preparation to receive the superstructure 
of a railroad; and even in the two most difficult of the passes, (where, in one case, deep cutting 
or a tunnel at the summit, near the surface, in rock, with heavy side-cutting and high embank- 
ments for short distances, and in the other a short cut of 60 feet—probably through rock— 
are proposed by Lieutenant Parke, to attain grades of 46 feet and 90 feet per mile, or less by 
increasing distance,) the natural slope of the ground may be used for a railroad for temporary 
purposes, and until the road itself can reduce the cost of materials and supplies to the lowest 
rates. 
The following table of distances and grades over the natural slopes, is given to show this. 
These two most difficult parts of the road are from 25 to 30 miles apart. In the Chiricahui Pass, 
the steepest natural slope is 194 feet to the mile for a distance of 24 miles. A twenty-four ton 
engine, on six drivers, can carry a load of 76 tons (2C0 passengers with 100 pounds baggage 
each) up a grade of 221 feet to a mile in the worst condition of the rail. 
In the pass through the ridge east of the Valle de Sauz, the steepest natural slope is 240 feet to 
the mile for a distance of three-quarters of a mile. A thirty-ton engine, on six drivers, will carry 
a load of 76 tons (200 passengers with 100 pounds baggage each) up a grade of 281 feet per 
mile. But the tunnel of three-quarters of a mile through rock near the surface, or cutting, may 
be preferable to using this steep slope. This natural slope of 240 feet to the mile for the distance 
of three-quarters of a mile, may be reduced to one of 200 feet to the mile, by a short cutting 
of 30 feet depth. The natural slope in the steepest part of the Chiricahui Pass being nearly 
200 feet to the mile, this cut would reduce these two passes to the same condition. These two 
points have been referred to not as presenting very great difficulties in construction, but merely 
from their being the only points on the line that appear to require any excavation and embank- 
ment, except of a trifling kind, to obtain grades generally in use on railroads, and to show that 
even here the natural slopes were such as might be used with but little preparation for the 
superstructure. 
It is probable that further examination will show that the pass of Puerto del Dado may be 
avoided by passing to the north of the Chiricahui mountains. 
The elevation of the camp near Fort Fillmore is 3,938 feet above the sea. The river between 
this and E] Paso is about 300 yards wide when confined to one channel, and presents no serious 
difficulty to bridging. The elevation at Molino, the terminus of Captain Pope’s survey, is 3,830 
feet; the distance between them 82 or 35 miles. 
Parke’s grades. 
From the Gila, 10 miles, 28.6 feet per mile, ascending. 
60 4c Uy “6 c 
12 “cc 93 “cr “ec 
19 “ec 50 “cc “ 
8 -** level. 
