AMERICAN GEOLOGY DECADE OF 1850-1859. 439 



shown to be erroneous, as he himself lived to recognize, 'fhus, 

 regarding the occurrence of gold, he wrote: 



[n general it may be said that the older the geological formation the greater the 

 probability of its containing valuable ores and metals. 



And further: 



There is room for doubt whether the great gold deposits of the world did not 

 originate exclusivelyin the Paleozoic strata, since we are not aware that the rocks 

 which have been proved to be of Azoic age have been found to be auriferous. 



In this, it will be noted, he followed the teaching of Murchison. 



To the reader of to-day it will seem scarcely possible that, at the 

 date of Whitney's writing - , there were no mines worked for silver 

 alone in the United States, the supply of the metal coming almost 

 wholly from the native gold of California. Argentiferous galena had 

 been worked to a slight extent, as at the Washington mine in David- 

 son County, North Carolina, but work was suspended at the time 

 of his writing. How little the silver resources of the West were 

 realized is shown by Whitney's comment on the rapid increase of the 

 gold output from year to year and the comparative decrease in that of 

 silver. He wrote: 



Silver is, in a geological point of view, the metal best adapted for a standard of 

 value, since, possessing all the valuable qualities which make gold suitable for that 

 purpose, it is not liable to those fluctuations in its production to which this latter is 

 exposed. There is no discovery of a new continent to he looked forward to whose 

 mines shall deluge the world with silver, and any increase in the amount of this 

 metal produced must come chiefly from the working of mining regions already 

 known. 



Yet Whitney himself lived to see the annual output of American 

 silver become so great as to practically remove it from the list of 

 precious metals and cause it to be rejected for all but subsidiary coinage. 



Whitney recognized the fact that none of the. deposits of lead in the 

 Mississippi Valley could be considered as coining under the head of 

 true veins (i. e., fissure veins), and that the productive deposits did 

 not generally exceed a hundred feet in thickness in the Galena (Lower 

 Silurian) limestone immediately overlying the Trenton. No ore of 

 consequence was known to occur in the so-called "Blue Limestone" 

 (Trenton, Bird's-eye, Chazy, and Black River) and it was not consid- 

 ered probable that the fissures would ever be found to extend through 

 the intervening sandstone into the Lower Magnesian beds. Sinking 

 through the sand into these latter beds was, therefore, considered as 

 mere random exploration and a foolish enterprise. 



He classified the ore deposits as (1) simple alluvial deposits which 

 were recognized as residual from the decomposing limestone; (2) 

 deposits in vertical fissures which had a very limited longitudinal 

 extent, and (3) deposits in flat sheets. All of these were regarded as 



