374 PROFESSOR J. A. EWING AND MK. \V. KOSKNHAIN 



the two will show the amount by which the crystalline grains have 



extended. 



Fig. 16. Strained Swedish iron. Magnified 300 diameters, vertical light. 

 Fig. 17. The same field as in fig. 16, with the same magnification, but seen under 



oblique light. The slip-bands on a few grains only are picked out as bright 



1 Kinds. 



PLATE 19. 



Fig. 18. Slip-bands developed on a glass-cast surface of lead when strained by 



bending. Magnified 100 diameters, vertical light. 

 Fig. 19. The same field as in fig. 18, seen under oblique light. 



PLATES 20 AND 21. 



Fig. 20. The same field as in figs. 18 and 19, seen under oblique light after the stage 

 carrying the specimen had l>een turned through alxmt 15. 



Fig. 21. Slip-bands in lead. 100 diameters, vertical light. 



Fig. 22. The same field as in tig. 21, seen under oblique light. 



Fig. 23. Slip-l>ands in lead, showing four intersecting systems. GOO diameters, 

 vertical light. 



Fig. 24. Slip-bands in lead. 1000 diameters, vertical light. The photograph shows 

 the straight slips and stepped intersections characteristic of this metal. 



PLATE 22. 



Fig. 25. Slip-bands in silver. Magnified 750 diameters, vertical light. 

 Fig. 26. Geometrical air-pits in glass-cast cadmium, slightly strained to show slip- 

 bands. 1000 diameters, vertical light. 

 Fig. 27. Ditto. 



PLATE 23. 



Fig. 28. Ditto. See also remarks on Figs. 7, 8, and 9. 



Fig. 29. Geometrical etched pits and slip-bands, produced by slight straining, in iron. 



750 diameters, vertical light. 



Fig. 30. Etched pits and slip-bauds in iron. 1000 diameters, vertical light. 

 Fig. 31. Polished and etched section of cold-rolled Swedish iron. 45 diameters, 



oblique light, showing the differences of brightness on various grains and 



the uniform brightness over each individual grain. 



