22 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
(5) Gold Belt of the Blue Mountains of Oregon, by W. Lindgren. 
This report is the result of an elaborate reconnaissance examination 
made by' the author in the summer of 1900 of an area somewhat over 
50 by 100 miles in extent. It shows the ability and thoroughness that 
characterize all of Mr. Lindgren's work, and will no doubt prove a 
useful source of information to those engaged in mining in that 
region. In actual scientific results such work is generally less fruit- 
ful than would have been the same amount of time and labor devoted 
to a smaller area containing well-developed mines. 
(6) Ore Deposits of Monte Cristo, Washington, by J. E. Spurr. 
This, the final report of the volume, is also in the nature of a recon- 
naissance, since the region had not been previously mapped geolog- 
ically and the available topography was on so small a scale as to afford 
a very imperfect base for his geological observations. His time was 
also limited; nevertheless, as the area was small (3^ by 4 miles), he 
was able to make as fairly complete a study of the deposits and 
map the geology in as much detail as the economic importance of 
the region demands. His general conclusions are, first, that the ore 
occurs mainly as replacements of certain igneous rocks and to a less 
extent as the filling of open spaces; second, that they have been 
deposited by descending waters, and hence that the best deposits will 
be found relatively near the surface. 
The other economic publications that have appeared during the 
year 1902 are: 
Bulletin No. 193. — Geological Relations and Distribution of Platinum and 
Associated Metals, by J. F. Kemp. 
This is an account of few known occurrences of platinum and 
associated metals throughout the world, based upon the published 
literature on the subject and supplemented, in the case of a few 
occurrences in this country and Canada, by personal observations of 
the writer. It contains also a discussion on the mineralogical asso- 
ciation and probable origin of these metals. 
Professional Paper No. 1. — Ketchikan Mining District of Alaska, with an Intro- 
ductory Sketch of the Geology of Southeastern Alaska, by A. H. Brooks. 
This is the first paper of a new series of quarto publications by the 
United States Geological Survey, authorized by the law of Congress 
of May, 1902, which confines the report of the Director to a single 
volume, and directs that these papers, like the bulletins, shall be dis- 
tributed gratuitously. It is a reconnaissance report on the present 
mining development of this large district of southeastern Alaska, 
which includes Prince of Wales Island and the adjoining mainland. 
It is accompanied by a sketch of the geology of those parts of south- 
eastern Alaska that have been visited by members of the Survey. 
