SOURCE OF THE ORE. 55 



evidence to justify tlie belief that cinnabar occurs on a large scale as 

 deposits coeval with the inclosing' rocks. Cinnabar is not known to exist 

 as cave-fillings. Several geologists think that cinnabar has been to some 

 extent siibstituted for sandstone, shale, or serpentine ; but, while this may 

 be true to some extent, this process does not seem to have been sufficiently 

 rapid to impress upon the deposits the peculiar character seen in some lead 

 mines. The hypothesis of the substitution of cinnabar appears to me thus 

 far to lack sufficient proof. 



Genesis and source of the ore. — Tlic mineral associatlons in which ciniuibar is 

 found seem to show conclusively that it has been deposited from solutions. 

 A very large part of the known deposits of cinnabar are extremely similar 

 in character, a fact which seems indicative of a similar origin. It is cer- 

 tain that some of the deposits are due to precipitation from hot volcanic 

 springs and it may fairly be inferred that many of them were formed in 

 this manner. The diversity of the country rocks in which the deposits 

 occur is evidence that only a part of them can have derived their metallic 

 contents from their own wall rocks; the remainder must owe their cinnabar 

 to some source between the point at which the waters acquired their heat 

 and the surface. Between the depth at whicli volcanic foci Tie and the 

 surface of the earth there must be substances of world-wide distribution 

 which frequently contain mercury in some form as an original ingredient. 

 These substances are probably massive rocks, and the only known rock 

 of correspondingly wide distribution is granite. 



I now pass to the geology of the cinnabar deposits of the Pacific 

 Slope. After describing them I shall return to the subjects mentioned in 

 these conclusions. 



