GEOLOGY. 63 



the Copper Caiion ore has been exported. There are rich 

 veins of copper-ore near Crescent City, in Del Norte county ; 

 but, with the present high prices of labor and coal, they cannot 

 be profitably wrought. Vitreous copper is found at William- 

 son's Pass, sixty miles from Los Angeles. 



§ 44. Coal. — The old red sandstone and the " true carbon- 

 iferous" rocks, as they are called, are wanting in Cahfornia ; 

 and it was long supposed that no valuable coal would ever be 

 discovered in the state ; but within the last year some veins 

 of a very good quality have been found near Mount Diablo. 

 The mineral belongs to the tertiary epoch, but contains far 

 more solid combustible matter and less incombustible material 

 than most tertiary coal. In the strict geological meaning of 

 the terms, it is not " coal," but " hgnite," belonging to a later 

 date than the true coal, and lying in a different formation. 

 The rocks are sandstone and shale, of the upper tertiary or 

 pliocene age, and were formed by alternating depositions in 

 salt and fresh water. The coal-veins are situated on the north- 

 eastern 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 substances, and 4 per cent, of 

 ashes. The coal is bituminous in character, breaks readily, 

 shows a bright surface where fractured, 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. 



§ 45. 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 sprimis, 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 



