lOOo. ! Solids under Mechanical Disturbance. 225 



PLATE 10. 



Fi<r. 7. Speculum mefal, the broad horizontal band is a very fine needle scratch 

 in which the particles of metal from the emery scratches have been 

 intercepted. 



Light, normal reflected, green screen. 

 Objective 3 mm. Oil immersion. Apochromat. N".A. 1'4. x 1500. 



!Fig. 8. Tool steel hardened and tempered showing flow of the metal during emery 



grinding. 

 Light and objective as in fig 7. x 775. 



Fig. 9. Speculum metal polished on rouged leather across the furrows left by fine 



emery, showing flow of metal across the furrows. 

 Light and objective as in fig. 7. x 775. 



Fig. 10. The same further polished. The outlines of the crystalline grains show 



under the surface. 

 Light and objective as in fig. 7. x 775. 



iFig. 11. The same with the surface film removed by KCy showing the grains 



surrounded by the eutectic. 

 Light and objective as in fig. 7. x 775. 



iFig. 12. The same again polished on rouged leather, showing the formation of a 



fresh film on the surface. 

 Light and objective as in fig. 7. x 775. 



All of Jthe above are from direct photographs without enlargement or reduction. 



