16 PROFILE. 
the relative elevations of not only the camps, the main summits or divides encountered and 
valleys crossed, but also the various intermediate accidents or changes in the surface passed 
over, the barometer being put up and reading taken at every apparent deviation from the 
uniform slope. 
No. 2, the upper, is constructed with reference to the sea-level, and shows the average grades 
with which the several sections of the route may be passed. The dotted lines being those at- 
tainable by deviating from the red line at points indicated, and following the blue, thereby the 
grades are improved and the line shortened; but at the same time tie question of water is 
thrown out of consideration, 
Commencing at the Rio Gila, we have from camp No. 10 a smooth, plain country extend- 
ing as far as camp No. 15, station 1, presenting a stretch of ninety-seven miles of easy grades, 
requiring but little work, the maximum grade being fifty feet per mile from camp No. 14, station 
1, to camp No. 15, station 1, a distance of nineteen miles. 
At camp No. 15, station 1, we entered a cañon leading from the Cienega de los Pimas, in the 
gap, by descending abruptly from the plain on its left bank to its dry sandy bottom. By a side- 
cutting this cation can be entered with a grade of nineteen feet. Reaching camp No. 16, the 
summit of the divide between the Cienega and the Hio San Pedro can be attained without 
trouble; but it is impracticable to continue on this line (the red) to the river. This difficulty 
can be overcome by deviating at camp No. 16, station 3, and following blue line through camp 
No. 17, station 1, and camp No. 17, station 3, and skirting along the bases of the hills bound- 
ing the valley to a point near camp No. 19, station 1, where, crossing the river, the ascent of 
the dry ravine leading from the range beyond is commenced. Through the cañon above camp 
No. 16, there will be required rock-cutting at points where, it becoming narrow and tortuous, 
rocky projections are presented as obstacles to either a right-line or gently curving trace. The 
walls of this cañon being, however, in no instance over eighty feet, and seldom over fifty feet 
high, and at many points, where it widens out to a valley, they are replaced by low, rounded 
hills, no insurmountable obstacle to an average grade of thirty-eight feet per mile is encoun- 
tered as far as the summit, camp No. 17, station 1. From this point, by pursuing the line indi- 
cated, the bottom of the San Pedro may be reached by a grade not exceeding sixty-one feet per 
mile, and will require but light cutting, the slopes of the foot-hills being of a loose clay. The 
river can be bridged by a single short span, the water-way being about twenty-five feet wide. 
Between the San Pedro and the Playa de los Pimas a low ridge intervenes, the approach to 
which is by a dry arroyo or drain leading from a gap in its crest, bounded by rounded hills and 
occasional walls, varying from twenty to fifty feet in height, made up of a semi-hardened con- 
glomerate mass of débris of granitic and volcanic rocks. In the gap there lies a rolling prairie- 
like country, extending in an unbroken plain down to the playa. This divide can be crossed 
with an average ascending grade of sixty-two feet, and a descending one not exceeding fifty- 
four feet. 
From the Playa de los Pimas the line crosses the Chiricahui range, passing through the 
Puerto del Dado. By the line travelled, the ascent to the summit of this pass lay over a smooth 
plain until reaching the foot-slopes of ilie mountains, when it became undulating, crossing val- 
leys and their divides; whereas by curving to the southward these foot-slopes will be avoided, 
and a continuously Sicinding slope is found, giving, after making a sixty-feet cutting at the 
summit, a grade less than forty-six feet per mile, that obtained by following the direct red and 
bluelines. Leaving the summit and following the red line, we find that in the distance 4.7 
miles to camp No. 22, station 1, a descent of seven hundred feet is made; and that thence to 
camp No. 22, station 4, distant seven miles, there is an additional descent of one hundred and 
eighty-one feet. The line in this descent crosses lateral ravines making from the summits 
on the right until reaching a point a few yards below camp No. 22, where it enters the main 
drain, and follows down its bed to the opening on the plain at camp No. 22, station 1. It 
thence passes to station 4, along the base of the ridge projecting eastward froin the Puerto. 
