14 ADAPTATION OF COUNTRY TO THE CONSTRUCTION OF A RAILROAD. 



tracted valley than below, the number of lateral ravines and streams are greater, requiring a 

 greater amount of masonry and earth work. The graduation, however, will be compara- 

 tively easy, for the cuts and fills will nearly balance each other, and a large majority of 

 the lateral ravines will require but small culverts or percolating drains, and many of them 

 none at all. There will be five first class bridges required across the San Lorenzo, the Salinas, 

 the San Antonio, the Nacimiento, and Pasa Robles creek. The materials for the construction 

 of the piers and abutments of these bridges are at hand at the respective places, though not of 

 a first rate character. Several smaller works of this character will also be necessary at several 

 points throughout the division. The line pursuing, for the most part, the windings of the valley, 

 is throughout a curved line ; but it is believed, from careful observation, and measurement where 

 practicable, that no curve of less than 4° will be required ; nor, indeed, throughout the entire 

 distance, from San Jose to Los Angeles, will a radius of less than 1,000 feet be necessary. 



The length of this division is *7l.50 miles. 



Maximum grade required, 70 feet jDer mile. 



Probable cost of graduation and superstructure, |3,5T5,000. 



Cost per mile, |50,000. 



Fifth Division.. — From Santa 31argarita valley to the mouth of Arroyo Grande. — This division 

 comprises, perhaps, the most difiicult and costly portion of the route, from the boldness of the 

 work required to overcome its difiiculties ; it contains the celebrated San Luis Pass through the 

 (Coast Range) Santa Lucia mountains, and is the only passable point of these mountains between 

 the Bay of Monterey and its southeastern extremity. The wagon road occupies this pass.* The 

 height of the summit is 1,556.5 feet above the level of the sea. The height of Santa Margarita 

 valley is 9Y8 feet, and the San Louis plain about an average height of 300 feet. The point 

 of tunnelling is two hundred feet below the summit, and at the foot of the cuesta or sharp divide 

 which lies between the disjointed mountains. To reach this point the line is projected on the slopes 

 of the hills on the west of Santa Margarita, and ascends with an uniform grade of eighty feet per 

 mile. This ascent will not be attended with any excessive cost of graduation, the side slopes of 

 the mountain being remarkably tenable, there being no gorges to fill, or wide valleys to span, and 

 presenting favorable cross sections for side cutting and embankments. The tunnel, three- 

 fourths of a mile in length, is through serpentine and sandstone rock, and can be advantageously 

 worked from both sides. In the construction of a road through this pass, should this tunnel b3 

 considered too formidable a work, there is no obstacle to passing this mountain, without cutting, 

 by a system of heavy grades, similar to those which have been worked so successfully for several 

 years -across the Blue Ridge at Rockfish Gap, where the traffic and travel of a great part of the 

 valley of Virginia has been carried over this mountain, over a grade of 275 feet per mile. To 

 accomplish the passage of the San Luis summit, there will be required a much less rate of 

 gradient, probably not over 200 feet per mile. On the west side of the cuesta the San Luis 

 creek heads, and descends rapidly to the plain through a wide valley, flanked on either side by 

 rib-like spurs from the mountain, which have a slope of about 30°, the alternating ravines 

 being, except in one instance, shallow ; four and one-half miles below there is a lateral ravine, 

 heading with a stream which flows through the plain to the ocean, called Corral de Piedras creek, in 

 a summit 1,191 feet above tide, and in the prolongation of the valley from the cuesta. A glance 



* A line of levels was run through this pass from Santa Margarita valley to the mouth of Arroyo Grande, but upon plotting 

 them they were found to have irreconcilable errors in them ; and as it would have involved a great loss of time to run a second 

 series to check these errors, it was not deemed advisable to do so. A longer series of barometric observations than we were able 

 to take, in connexion with these levels, would have been necessary to institute comparisons between these several modes of 

 determining elevations. 



