-li'.i; On (In Tnni Iron hardened by Overstrain. 



All the results which are described alx>ve for steel were also obtained 

 with Lowmoor iron. The hardening by overstrain and the tempering 

 of soft Lowmoor iron only differed in detail from the analogous harden- 

 ing and tempering of steel. 



The iron and steel employed in this research were also examined, 

 when in various conditions of hardness, by means of the microscope, 

 and micro-photographs are reproduced in the paper. The ordinary 

 methods of relief polishing and of etching by dilute nitric acid were 

 employed, and a new method of staining steel, by rubbing with ordi- 

 nary moistened cocoa, was made use of and is described in the paper. 



