DEPARTMENT OF GEOLOGY 
45 
Ideal relief of a complete glacier. 
Ideal relief illustrating the formation of valleys by erosion. 
Ideal relief of a volcanic island. 
Ideal relief of a steep coast and dune coast, showing the two 
principal types of sea coast as they appear at ebb tide. 
Geological relief map of Mount Aetna. 
Geological relief map of the Island of Bourbon. Scale, 
I : 300,000. 
Geological relief map of Blair, Bedford, and Huntingdon 
counties, Pennsylvania. A portion dissected to show geological 
structure. 
Relief map of a part of Mount Desert Island, Maine. Scale, 
I to 40,000. 
Relief map of Mont Blanc. Horizontal scale, K-inch equals 
I mile. Vertical scale, iK inch equals i mile. 
Relief map showing irrigation system at Ontario, San Ber- 
nardino county, California. 
The relief map of the moon exhibited in the alcove at the 
entrance to the Department may also properly be considered a 
part of this collection. 
A complete series of the topographical maps issued by the 
U. S. Geological Survey can be consulted on application to the 
Curator. 
ECONOMIC GEOLOGY. 
It is the purpose of the collections shown in this Division to 
illustrate modes of occurrence in nature of the minerals and ores 
which have economic importance, to show the localities from 
which they are obtained, the processes used in their extraction 
and treatment, and their application to human arts and indus- 
tries. The collections may conveniently be classified into five 
groups, which can be most readily inspected in the order 
named : 
Building stones and quarry products. Hall 67. 
Clays and sands. Hall 68. 
Carbon minerals, including coals, petroleum, etc., Halls, 69, 
70 and 71. 
Ores and products of the precious metals and lead. 
Ores and products of the base metals. Hall 79. 
Salts of the alkalies and alkali earths, Hall 78. 
