26 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [buiZ. 213. 
be of much value in directing the explorations of those engaged in 
mining. It will be chiefly valuable in furnishing a record of the 
immense ore bodies that have been mined in the district during the 
last twenty-five years, in showing the possibilities and limits of geo- 
logical induction by contrasting their actual geological relations with 
those predicated in the first report from such facts as were open to 
observation. It will also afford further data for testing and modify- 
ing the theories of ore formation propounded in that report. Circum- 
stances are such that it is impossible to determine when this report 
will be ready for publication. 
IDAHO. 
Mineral deposits of flu Bitterroot Range and Clearwater Moun- 
tains. — In the summer of L899 Mr. Lindgren was engaged in making 
a geological reconnaissance in those parts of Idaho and Montana lying 
north of the Salmon River and extending from the Bitterroot Vallej 7 
westward to the lava plains of the Columbia. In the course of this 
work he observed the scattered ore deposits that are developed in this 
region, without, however, having time to make an exhaustive study 
of them. The area is largely of granite, with some sedimentary quarts 
zites, slates, and limestones, principally upon the borders. It is 
notable thai in the central part of the granite area no important ore 
deposits have yet been discovered. In the subsequent pages Mi'. 
Lindgren gives an interesting summary of his observations and of the 
structural relations of the various deposits observed. 
MISSISSIPPI BASIN. 
Studies have been made during the summer of 1002 in the Missis- 
sippi Valley region, first, of the lead and zinc deposits of northern 
Arkansas by G. I. Adams, and, second, of the lead and zinc deposits 
of the Joplin district of Missouri and of the lead, zinc, and fluorspar 
deposits of western Kentucky by W. S. Tangier Smith. 
All these deposits belong to a general type geologically distinct from 
those found in the mountains of the West, and are of special interest 
on that account. Brief summaries of the results thus far obtained 
will be found on later pages of this volume. 
MONTANA. 
Copper mines of Butte. — The first study of the extremely important 
vein deposits in granite at Butte Mountain was made in the summer 
of 1896, and the results were published in folio form the following 
year. Not long after the completion of this report, as a consequence 
of litigation which sprung up between the most important mining 
companies of the region, a great deal of underground exploration was 
done for the express purpose of ascertaining more accurately the geo- 
