Whitney's Geology of California, 361 
centage of copper. Copper mines occur in various other places 
in the State. Some in Plumas county promise well, and others in 
el Norte county have sent some ore to market of great richness ; 
but thus far the yield of all the other mines has been insignifi- 
cant compared with that from those of Calaveras county. The 
shipments of ore from the State have been as follows: 
1863, - - - 5,933 tons, valued at $512,925 
1864, - - - 14,325 “ “4 1,094,660 
e news- 
papers state that the Union mine shipped an average of 1000 
lower, the passes lower, the granitic core of the chain narrower, 
the belt of metamorphic rocks on the western slope correspond- 
re mil ut large 
In these larger areas of 
caped the usual metamorphism. , 
We are now led naturally to consider the question of the age 
of the rocks of the auriferous series in California. They have 
been regarded as older than the Carboniferous by all writers 
on the subject previous to the publication of the Reports un- 
der consideration. The announcement, therefore, of their later 
ew 
ogis 
paleontological evi- 
