24 
CONCLUSION OF THE OFFICIAL REVIEW, ETC. 
heaviest portion of the work for this distance of one hundred and seventy-seven miles. The 
maximum grade required will he seventy feet per mile, for two miles. 
A month was devoted to a thorough examination of the headwaters of the Salinas river. 
Reconnoitring parties were sent forward to examine the main stream and its largest tributary, 
the Estrella and the Cuyama plain, or valley of the Rio de Santa Maria, beyond, while a detailed 
survey of the San Luis pass was being made. The explorations about the heads of the Salinas 
and the Cuyama plain prove that a line through this country would be impracticable. An 
extensive basin was discovered—the Llano Estero—a tributary to the Tulare valley, which 
affords a very favorable pass from that valley to the bays of Monterey and San Francisco ; the 
elevation of the summit being about 1,800 feet above the sea. The approach from the Tulare 
valley is over a plain for about forty miles. The distance from this pass to Kern lake is sixty- 
five miles. 
The elevation of the lake above the sea, according to Lieutenant Williamson, is three hundred 
and ninety-eight feet. It is believed that a grade of sixty feet per mile will accomplish the 
descent from the summit, westward, to the Estrella. The average grade of Estrella creek to 
its mouth at San Miguel is about twenty feet per mile. 
The route was continued across the Santa Lucia mountains, through the San Luis pass, to 
the seashore. A detailed survey of this pass was made. It is a sharp divide, composed of 
slightly metamorphosed sandstone and serpentine rock. The elevation of the summit was found 
to be 1,556 feet above the sea. It is proposed to tunnel this pass for three-fourths of a mile, 
commencing at a point about 200 feet below the summit. The maximum ascending grade would 
be 80 feet per mile. The San Luis creek heads on the seaward side of this pass, and descends 
rapidly to the plain through a wide valley, flanked on either side by rib-like spurs from the 
mountain. The descent of the stream is too great to admit the location of the road through or 
near San Luis Obispo ; but, four and a half miles below its source, there is a lateral ravine, 
from the summit of which the line may be carried along the slopes of the mountains to the small 
divide between Corral de Piedras creek and Arroyo Grande, a stream running to the Pacific, 
whose slope, from the point where it is reached, admits of railroad location as far as its mouth. 
From the summit of the San Luis pass to the ocean, a grade of 100 feet per mile would be 
required for fourteen miles. This section constitutes the boldest feature of the route between 
San Francisco and Los Angeles. Lieutenant Parke is of opinion that for temporary purposes 
this pass can be surmounted without a tunnel, by resorting to a system of short curves and 
heavy grades—the greatest 200 feet per mile—similar to that adopted in the location of the 
Virginia Central Railroad across the Blue Ridge at Rockfish Gap, where the maximum grade 
is 275 feet per mile. The examinations in the vicinity of San Luis Obispo having been completed, 
the region lying between the ocean, the plains of Los Angeles, the western edge of the Great 
Basin, and the heads of the Tulare and Salinas valleys was thoroughly explored. The line 
adopted as most favorable commences at the Arroyo Grande ; traverses the Guadalupe Largo ; 
ascends the Todos Santos summit; descends to the Rio de Tres Alamos ; crosses the spur between 
Rio de Tres Alamos and the Santa Inez river; passes to the summit of the Gaviote pass at Santa 
Cruz—elevation, 700 feet—and, through the lower portion of the Gaviote pass and creek, to the 
coast. The maximum grade upon this line is 100 feet per mile, for 5| miles, through the 
Gaviote canon. From the summit of the Gaviote pass (at Santa Cruz) to the ocean, the location 
will be bold ; requiring heavy work in earth and rock (sandstone) to keep up the grade. A 
lofty structure will be required across the Gaviote creek, and a heavy cut through a salient 
