344 RESOURCES OF CALIFORNIA. 



tible material, than most tertiary coal. In the strict geologi- 

 cal meaning of the terms, it is not " coal," but " lignite," be- 

 longing to a later date than the true coal, and lying in a dif- 

 ferent formation. The rocks are sandstone and shale, of the 

 cretaceous or upper secondary age, and were formed by alter- 

 nating depositions in salt and fresh water. The coal veins are 

 situated on the northeastern slope of Mount Diablo, are from 

 two to nine feet in thickness, dip to the north at an average of 

 30, and open on the southern declivities of the hills. A 

 chemical analysis of some of the best specimens showed 50 

 per cent, of carbon, 46 per cent, of volatile bituminous sub- 

 stances, and 4 per cent, of ashes. The coal is bituminous in 

 character, breaks readily, shows a bright surface where frac- 

 tured, and burns with a brilliant flame. The quantity is 

 large, and it can be profitably supplied in San Francisco at 

 eight dollars per ton, whereas imported coal has hitherto cost 

 twice as much. 



274. Asphaltum. Bituminous springs are numerous near 

 the coast, from the northern line of Monterey County to San 

 Diego. They throw up a dark, pitch-like fluid, of a strong 

 odor, which, on exposure to the air, grows thick, and finally 

 solid. It collects in great masses about the springs, and in 

 some places covers several acres of ground. After being ex- 

 posed to the air for some time, it is called " asphaltum," which 

 is very hard in cold weather, but grows soft at about 75, and 

 becomes liquid at 85. Some springs of it rise in the sea near 

 San Diego, and others near Santa Barbara ; and masses of the 

 asphaltum are seen floating many miles from shore. The air 

 at sea is even scented with it, and on several occasions frights 

 on shipboard have been caused by its odor, which was sup- 

 posed to come from some hidden fire. 



The principal places in which these springs of asphaltum are 

 found, are the following : 



1. In the Santa Cruz Mountains, in the southeastern part 

 of Santa Clara County. A tract of twenty-five acres is here 

 covered by the hardened asphaltum. 



