no 



BELL SYSTEM TECHNICAL JOURNAL 



Fig. 4 — Mag. 3500X. Fig. 4 shows a somewhat later period in development of 

 troostite. The troostite appears to have formed along grain boundaries. The excess 

 constituent is clearly seen, and here and there a laminated structure, pearlite. Evi- 

 dently whatever the state of the carbide with reference to the iron in troostite — 

 wnethei contained in solid solution as first formed or whether disposed as a fine aggre- 

 gate with the iron — the condition must be very unstable, otherwise evidences of finely 

 laminated pearlite would be lacking. 



