

"\ Till: CUYSTALUXK STWCTriJK uK MKTAl 373 



EXPLANATION UP FICUKKS ON THK PLATEW. 



I'I.ATKS 15-28. 

 I'LATK 15. 



Fig. '2. Nearly pure commercial iron (transformer plate). |H>lished uiul etched. Mag- 



mlied _'()() diameters, vertical illuiniiiiition. 

 Fig. :}. Photograph of l)isnnitli crystals, from a specimen in the < 'ambridge University 



Mineralogical Museum, iftlis of full size. 

 Kig. I. Facets on a crystalline grain of iron, produced by etching. These facets give 



rise to differences of brightness when the grains are seen under oblique 



illumination. Magnified 1500 diameters, vertical light. 



PLATE 10. 



Fig. 5. Etched pits in Swedish iron. 1000 diameters, vertical light. 



Fig. <>. Surface of cadmium cast against glass, showing crystalline boundaries empha- 



si/rd by air-channels. 100 diameters, vertical light. 

 Fig. 7. Air-pits on a glass-cast surface of cadmium. 1000 diameters, vertical light. 



Pits are shown on three crystals, having a different shape and orientation 



on each. 



PLATE 17. 



Fig. 8. Air-pits on a glass-aist surface of cadmium. 1000 diameters, vertical light. 



The pits are surrounded by halos due to the absorption of smaller bubbles 



by the pits. 

 Fig. '.). Similar pits to those in tigs. 7 and 8, but more highly magnified 4200 



diameters. The photograph shows that the pits have geometrical inner 



faces. 

 Fig. 10. Air-pits in glass-cast tin. Magnified 1000 diameters, vertical light. The 



irregularly oriented black patches are crystals of an impurity. 

 Fig. l_. Slip-bands in Swedish iron strained by tension. 400 diameters, vertical 



light. The photograph shows a feature that is frequently observed, viz., a 



tendency in the lines to become curved near the inter-crystalline boundaries, 



suggesting the existence of keyed steps at the boundaries. 



PLATE 18. 



Figs. 13 and 14. Two views of the same crystalline grains in iron before and after 

 straining. Magnified 200 diameters, vertical light. Close comjwrison of 



