40 PROCEEDINGS OF THE AMERICAN ACADEMY 



LIST OF ILLUSTRATIONS. 



Prehistoric. Found on the altar of an Indian mound in Ohio, 



U. S. A. 

 LaCaille. Etched face cut parallel to an assumed cube plane, and 



showing in section plates parallel to the regular dodecahedron octa- 

 hedron and twin octahedron. 

 Coahuila or Butcher Iron. Printed directly from an etched slab 



of the meteorite, showing Neumann lines. 

 Coahuila or Butcher Iron. Enlarged sketch, a cleavage crystal, 



a portion of a twin cube, with an octahedral modification. 

 Coahuila or Butcher Iron. Cleavage crystal showing how the 



Neumann lines can all be referred to a cube with twin members on 



all of the trigonal axes. 

 Putnam County. Etched face of a natural octahedron, showing 



Widmanstiittian plates, and at the same time a granular structure. 

 Careyfort, De Kalb County. Showing the etched figures on a 



surface cut parallel to a natural octahedral face. 

 Braunau. Showing twinning lines as they appear on a natural cube 



face. 

 Cranberry Plains. Two faces of a natural octahedron, showing on 



one side bent plates, and on the other only a mottled surface. 

 Knoxville, Tazewell County. An etched face, showing verj' fine 



octahedral crystallization. 

 Coopertown, Robertson County. Showing etched figures on an 



octahedral face, and a face cut at right angles. The plates lettered 



a are cubic, those lettered b dodecahedral, and the rest octahedral. 

 Fig. 12. Russel Gulch. Printed directly from an etched slab, showing bent 



Widmanstattian plates. 

 Fig. 13. Frankfort, Franklin County. Large cleavage octahedron. 

 Fig. 14. Barranca Bianca. Etched face, showing very striking figures. 

 Fig. 15. Butler, Bates County. Shows an etched face with Widmanstattian 



figures, extending to the finest Neumann lines. The small figure 



at the left, shows one face of a very perfect cleavage octahedron 



with octahedral and dodecahedral markings. 

 Fig. 16. Mica from Chandler's Hollow, Delaware, with depositions of 



magnetite along the planes of crystalline growth, showing the 



formation of figures similar to the Widmanstattian, by the exclusion 



of foreign material in the process of crystallization. 



