14 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
boundaries shown are not final and will undoubtedly be somewhat 
changed when the field work in this region is completed. 
To Mr. S. F. Emmons, geologist in charge of the investigation of 
metalliferous deposits, my thanks are due for various helpful sugges- 
tions and criticisms and for access to his unpublished notes on the 
Yankee Girl and Guston mines. 
The descriptions of the abandoned mines of the Red Mountain dis- 
trict would be far more imperfect than they are were it not for much 
information courteously supplied hy Mr. Bedford McNeill, of London, 
liquidator of the New Guston Company; Mr. T. E. Schwarz, of Den- 
ver, and Mr. Otto J. Schulz, of St. Louis, trustee of the Genesee- 
Vanderbilt mines. 
To the mining men of the region I am indebted for much cordial 
assistance and for courtesies which have many times been recalled 
with pleasure. 
GEOGRAPHICAL POSITION. 
The Silverton quadrangle, embracing one-sixteenth of a square 
degree of the earth's surface, lies between the meridians 107° 30' and 
107° 45' west longitude and the parallels 37° 45' and 38° 00' north lati- 
tude. On the west it adjoins the Telluride quadrangle and on the 
south the Needle Mountain quadrangle. Its area is approximately 
235.3 square miles. It lies in southwestern Colorado, in the highest 
and most rugged portion of the San Juan Mountains, including a 
part of the continental divide. There are comprised within its bound- 
aries the headwaters of the Animas River and portions of the head- 
waters of the Rio Grande, Gunnison, Uncompahgre, and San Miguel 
rivers. The principal settlement is Silverton, a town of about 900 
inhabitants. The position of the Silverton quadrangle with reference 
to the adjacent map units of the Geological Surve) 7 is shown in the 
index map, PI. II. 
LITERATURE. 
The published literature relating to that portion of the San Juan 
Mountains included within the Silverton quadrangle is not voluminous. 
It is chiefly comprised in the official reports of the members of the 
Hayden surve} T , who visited the region in 1874, 1875, and 1876; in 
descriptive notes of various travelers through the San Juan; in scat- 
tered descriptions of mines and minerals occurring in the district, 
and in references to the history of mining development found in the 
more general works on Colorado and its resources. The following 
bibliography includes most of the important publications concerning 
the Silverton region. The data contained in them have been freely 
used in the p reparation of the following historical sketch, for the 
purpose of su£>plementing information obtained at first hand from 
those who actually participated in the development of the district. 
