250 OX FKACTURE OF METALS UXDER REPEATED ALTERXATIOXS OF STRESS. 
PLATES 8 AND 9.‘ 
Figs. 7-8. Fatigue of Swedish iron by reversals of a stress of 12’3 tons per sq. inch. 
Maeiiification 150 diameters. 
Fig. 7 after 170,000 reversals. 
Fig. 8 same after re-polishing and re-etching. 
Figs, 9-12. Fatigue of Swedish iron by reversals of a stress of 12’4 tons per sq. inch. 
Mao;nification 1000 diameters. 
Fig. 9 after 1,000 reversals. 
Fig. 10 after 2,000 reversals. 
Fig. 11 after 10,000 reversals. 
Fig. 12 after 40,000 reversals. 
Fig. 14. Another part of the same specimen after 160,000 reversals. 
Development of a slip-band by 3,000,000 reversals of a stress of 6’9 tons 
jDer sq. inch. 
Fig. 15. 
