108 VARIOUS LOCALITIES OF ASPIIALTUM. 



asphaltic rocks lie beneath high water mark, and are visible at low water ; nor is the effusion 

 of bitumen from submarine localities confined to this district. The waters of the Santa Bar- 

 bara channel are frequently covered with a thin layer of liquid bitumen, which is gradually 

 inspissated by the evaporation and cifect of solar heat, and then washed ashore in solid masses 

 by the tide; the whole atmosphere of the sea, many miles out, being highly impregnated with 

 the bituminous odor. These phenomena (the odor and surface film) were observed by the 

 writer on two several occasions in sailing between San Diego and San Luis Obispo. It has 

 also been observed still further out at sea by Lieut. Trowbridge,* U. S. A. It has not, how- 

 ever, been observed along the route of the Panama mail steamers, whose track lies considerably 

 west of the islands off Santa Barbara shore, so that it may be inferred that the greater amount 

 of upheaving action which evolves bitumen lies between these islands and the coast. 



This substance exists in all the stages of consistence, from that of a thin syrup to that of 

 ordinary coal. In some deposits, as along the Buenaventura river, all of these are found 

 together ; also along Tar creek, a tributary of the Santa Clara ; in fact, wherever the bitumen 

 is oozing at the present moment there the substance is fluid and thin. The quantity of the 

 mineral is incalculably great in the several deposits, and the supply appears to be steady, 

 although not abundant in the majority of the localities. The characteristics of each locality 

 will be briefly alluded to in detail. 



1. The bitumen of the Santa Cruz mountains, near the Faj'aro river-. — It is here found on the 

 banks of the Arroyos La Brae and Pescadero. As many as six springs were found close to the 

 banks of these two creeks, which cut their way through soft brown fossiliferous sandstone. 

 The ground for several yards round each spring was covered with the solidified mineral, and, 

 perhaps, twenty-five acres in all were occupied by the overflow. The fluidity of the bitumen 

 at the immediate spring was not very great ; not far distant from these is the igneous rock of 

 the Santa Cruz range, serpentine and trap, (greenstone,) which is directly in contact with the 

 tertiary sandstone, the latter is metamorphic near the point of contact. 



2. Bitumen of San Luis valley. — This deposit is situated about four miles southwest of the 

 village of San Luis Obispo, along the road leading down the river to the port. The road, as it 

 leaves the valley, passes between a series of low hills, which cut off the valley from the shore. 

 About half a mile below the ranch Corral de Piedras, which is located close to the edge of the 

 valley, the asphalt is met with in situ. The rock is a fine quartzose sandstone of a brownish 

 color^ and decaying under the finger, darker on the surface than inside, and forming a pepper- 

 gray colored soil ; this bed is not fossiliferous. The strike, north 70° west, crosses the road, 

 the rock dipping southwest 20°. The bitumen here oozes out from the rock fissures, and 

 is spread over a space of 350 yards from the creek ; one opening has a basin diameter of 

 30 inches ; 8 inches below the surface is the well of bitumen, which rises and flows over the 

 edge, coursing down toward the creek in a small stream, which solidifies some distance below, 

 forming a layer of pitchy hardness, over which the fresher outflow wends its way. Another 

 spring, 20 inches in diameter, resembles the former, being a hole in the superficial sand rock. 

 This well has the bitumen in a more fluid condition ; a six foot pole was pushed down through 

 the centre of this fluid mass, and found its way readily until, from its pliancy, it no longer 

 resisted pressure. The liquid hardens readily at the edges of the spring and on the soil around, 

 which is partially liquified by the mid-day sun, rendering it plastic, but not fiuid. A third 

 spring close by gave off carburetted hydrogen gas, which was inflamed and burned brilliantly 



* On the authority of Dr. TrasU'a " lleport uu Guulogy of Coast Mountains." 



