68 
apart, horizontal galleries run from the shaft and connect at inter- 
vals with other passages. Figures of miners at work may be 
seen by looking through these cross-ways from the ends of the 
model. 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 galleries, 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, Minn. 
Case 2. — The extraction of iron from its ores by the blast 
furnace. The material fed to the furnace and given out by it is 
shown, also a series of pig irons showing the characteristic frac- 
tures of the different grades. 
Cases 2 and 3 B. — Alloys of iron used in iron working. 
Cases No. 3 A and 4 A.— A collection illustrating the 
methods of testing structural iron and steel. In general a piece 
of steel is broken and the strain at which it yields is noted. Other 
pieces are bent hot and cold and their behavior in respect to 
cracking is noted. At the ends of the cases are specimens show- 
ing the successive stages of rolling an ingot into a rail or beam, 
also the method of crushing a number of bars or of iron 
into one solid beam. 
Case 3 C, — Fibrous fracture of wrought iron. 
Case 3 D. — “Crystalline” fracture of wrought iron. 
Case 4 C. — Malleable cast iron. This is a cast iron the sur- 
face of which has been decarbonized and thus transformed into 
wrought iron by the action of oxide of iron at a high temperature. 
Case 4 B, — Direct process wrought iron. The example 
shovm is over 2000 years old, and was made directly from the ore 
without passing through the stage of pig iron. 
Cases 4 C and D. — Fractures and test pieces of open hearth 
steel from Avesta, Sweden, showing the variation of texture and 
strength with the composition. 
A bar of open hearth steel in which a knot has been tied cold, 
as a test of the quality of the material stands upon the wall by 
the side of this case. 
Case 5. — Sections of steel bars, rails and structural beams, 
from Spain, donated by Sociedad de Altos Hornos y Fabricas de 
