emmons] INVESTIGATION OF METALLIFEROUS ORES. 25 
CALIFORNIA. 
Shasta County. — The copper deposits around the head of the Sac- 
ramento Valley in California have been assuming considerable 
economic importance of late years, and as they present a somewhat 
different type from those hitherto studied it has been judged wise 
to make a special study of them. In preparation for this work 
J. S. Diller was engaged during the summer of 1902 in making an 
areal survey of the Redding quadrangle, which includes the most 
important copper deposits. He has prepared a brief summary of 
the results of his work, showing the general geological relations of 
the deposits. Detailed topographic maps are now being prepared 
of the smaller areas, in which the most important ore bodies occur, 
preparatory to special economic surveys, which will be made as early 
as practicable. 
Neocene river systems of the Sierra Nevada. — A very large pro- 
portion of the gold product of California is derived from gravels 
deposited in the beds of rivers belonging to an ancient system of 
drainage quite distinct and independent of the present river system 
of the Sierra Nevada. These gravels are now buried beneath more 
recent deposits and lava flows, and it is of great importance to miners 
to be able to trace their probable position in still undeveloped areas. 
In the course of his areal studies of the geology of the Sierra 
Nevada Mr. Lindgren had accumulated a great many facts concern- 
ing the location of these ancient river beds, parts of which had been 
studied and mapped by the able engineers in charge of various large 
hydraulic mining undertakings. During the summers of 1901 and 
1902 Mr. Lindgren was able to devote part of the time allotted to 
field work to a further examination of the Sierra Nevada region for 
the special purpose of supplementing his previous observations so as 
to give a comprehensive view of the whole river system and to 
enable him to map the probable course of the earlier or Neocene 
rivers. In this study, which is largely of a physiographic nature, he 
has been efficiently aided by J. M. Boutwell. It is a work which 
necessarily requires very careful platting and much deliberate con- 
sideration. It will be prepared for publication as rapidly as the 
press of work admits. Its condition is more fully described by Mr. 
Lindgren on later pages. 
COLORADO. 
In Colorado no new economic surveys have been commenced during 
the last three years. The writer, assisted by J. D. Irving, has con- 
tinued the gathering of data for a supplemental report on the geolog}^ 
of the Lead vi lie district during such time as could be spared from his 
regular duties of supervising the work in other fields. This work 
will be mainly of scientific interest, as at this late day it can hardly 
