498 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 5<> 



Plate LXVIII 



Fig. i. Moraine-like hills on outer slope of northern rim of crater. 



2. Near view of interior walls of crater, with talus and alluvial fans 

 from the cliffs. 



Plate LXIX 

 View in interior of crater showing nearly level floor; looking south. 



Plate LXX 

 View in interior of crater showing a near view of south wall. 



Plate LXXI 

 Microstructure of gray sandstone 



Fig. i. The unaltered sandstone. 



2. First and partial phase of alteration. 



3. Completely metamorphosed sandstone. 



4. Quartz glass formed by fusion of sandstone. 



5. A highly magnified portion of No. 3, showing curved cleavage lines. 



Plate LXXII 

 Altered sandstone from shafts inside of crater 



Fig. 1. Completely metamorphosed sandstone, with secondary platy structure 

 at right angles to bedding. 



2. Fused and slightly pumiceous sandstone, almost wholly glass. 



3. Pumiceous sandstone, almost wholly glass. 



4. Coarsely pumiceous sandstone, almost wholly glass. 



Plate LXXIII 

 Typical forms of Canyon Diablo meteoric irons 



Plate LXXIV 

 Etched section of Canyon Diablo iron 



Plate LXXV 



Shale-ball irons from trenches on north rim of crater 



Fig. 1. Ball consisting of residual nucleus of metallic iron, with adhering frag- 

 ments of sandstone and limestone. 

 2. Shale ball cut in halves and showing metallic nucleus, with its crust of 

 iron shale. 



