many times by means of renewed upheaval, besides the additions 
which have been made to its crest in the form of volcanic ma- 
id 
terial. Were the Sierra to receive no accessions of any kind, and 
therefore gradually yield to the process of erosion, the moisture 
laden winds from the Pacific would no longer meet a barrier 
bevond which they can carry only a trifling quantity of moisture, 
and the desert regions of the interior would be again well watered 
as we know them to have been during portions of the later geo¬ 
logical periods. It is not likely that this happy change will soon 
occur for at present the Pacific coast appears to be rising. 
Before passing to another subject I desire to point out that 
though the conditions in the Sierra Nevada and along the coast 
ranges of California are such that no movements along their 
fault lines during the Archaean can now be demonstrated, there 
are indirect reasons for believing that these lines of disturbance 
like those to the east of them existed before the Palaeozoic, and 
that all the more important portions of the fissure system which 
has helped to determine the position of the present mountain 
system were established in the remote antiquity of the Archaean. 
The Pacific slope is most famous for its mineral riches and it 
was noticed twenty years since that the mines lie in belts parallel 
to the general trend of the mountains. At that time information 
was too scanty either to define these belts, or to correlate their 
occurrence with the general geology of the region. Somewhat 
recently this subject has been taken up again with the advantage 
of more detailed knowledge. There are it appears four great 
belts of ore deposits. One of these coincides with the great 
Wahsatch fault. This produces the lead and silver of Utah. 
The second runs diagonally through Arizona fron S. E. to N. W. 
and pursues a northerly course through Nevada. It coincides 
with the line upon which disturbance took place first in the 
Archaean and again at the close of the Jurassic. The third ore 
belt is the gold belt of California lying on the western flank of the 
Sierra Nevada. This immensely productive chain of ore deposits 
lies along the fault which took place early in the Cretaceous. 
The last belt is that in which all the important quicksilver mines 
of the United States are situated. It lies near the coast of Cali¬ 
fornia in the strip of country which underwent such violent dis- 
