REVIEWS 721 
of the Coal Measures of Indiana; Part III, with the Detailed Geology 
of the Indiana Coal Field; and Part IV, with Mines, Mining, and the 
Utilization of Coal. In Part III the method of treatment is by coun- 
ties. 
Probably the best feature of the report is to be found in the excel- 
lent illustrations, which consist of 986 figures, g1 plates, and 7 maps. 
Especially are the maps and the accompanying sections to be com- 
mended. 
The latter part of the volume is devoted to reports of the inspector 
of. mines and the natural gas supervisor. 
A. H. PURDUE. 
UNIVERSITY OF ARKANSAS, 
Fayetteville, Ark. 
United States Geological Survey. Monograph XXXT. Geology 
of the Aspen Mining District, Colorado, with Atlas. JOSIAH 
EpWARD Spurr. Samuel Franklin Emmons, geologist in 
charge. 
The monograph is primarily concerned with the economic interests 
of the Aspen district. But it also contains much that is of general 
scientific interest. Mr. Emmons contributes the introduction, but the 
body of the monograph is the work of Mr. Spurr. The volume is 
profusely illustrated and the accompanying atlas contains sheets giving 
the general geology and topography of the district, besides eight special 
sheets giving the detailed geology of limited areas. It also contains 
numerous sections constructed on an elaborate scale, which make the 
complex faulting intelligible. Both the monograph and its accompany- 
ing atlas exemplify the magnificent execution characteristic of the 
United States Geological Survey. 
Great interest attaches to the author’s study of faults as set forth in 
this work. Aspen seems to have furnished a field quite worthy of his 
best endeavor. Some of the sheets presented in the atlas seem like 
inextricable puzzles; but this special student of faults straightens out 
the “crazy-work”’ in an admirable way and makes it all intelligible. 
It is of interest to note the fact that movement along some of the fault- 
ing plains is taking place at the present time at a rate which requires 
recognition in the practical operations of mining. 
