DEPARTMENT OF GEOLOGY 
43 
From the two main galleries, sloping ways, not shown in the 
model, lead upward to passages at higher levels which do 
not connect with the shaft. Here as the ore is excavated it 
is thrown through chutes to the tramways of the main gal- 
leries, and there taken by ore cars to the shafts and raised to 
the surface. The timbering is to prevent the top and sides 
from caving. 
Upon the wall is a large painting representing a section of 
the Soudan mine of Tower, Minnesota. 
Hall 77. 
Passing into Hall 77, and turning to the right, maps will be 
found against the wall in the following order : 
Relief map of the Isthmus of Panama, showing the proposed 
course of the canal. 
Map of the Isthmus of Panama. 
Model showing methods of irrigation on steeply and gently 
sloping fields. 
Geological relief map of the Island of Palma. 
Relief map of the Drainage basin of the Arkansas river in 
Colorado, showing the relations of the catchment basins to the 
reservoir sites and irrigable lands. The entire area drained by 
the Arkansas river from its source in the High Rockies to the 
plains of eastern Colorado is shown. 
Relief map of Europe. Horizontal scale, 85 miles to i inch. 
Vertical scale, 45 times the horizontal. 
Relief map of Asia. Horizontal scale, 216 miles to i inch. 
Vertical scale, 39 times the horizontal. 
Relief map of Africa. Horizontal scale, 184 miles to i inch. 
Vertical scale, 53 times the horizontal. 
Relief map of North America. Horizontal scale, 140 miles to 
I inch. Vertical scale, 39 times the horizontal. 
Relief map of South America. Horizontal scale 147 miles to 
I inch. Vertical scale 30 times the horizontal. 
The foregoing five maps permit study to advantage of the 
great features of continental relief. Among those that may be 
noted are: That the continents in general have elevated moun- 
tain borders and a low or basin -like interior; that the highest 
border faces the larger ocean; that the lines of greatest elevation 
are placed outside the center; that all the gentle slopes descend 
toward the Atlantic and the Frozen ocean, all the steep ones 
