ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 591 



ingot with 1*01 p.c. manganese, 0'28 p.c. sulphur, contained only 

 the dove-grey manganese sulphide. The existence, at some stage in 

 the solidification of the steel, of a eutectic of iron and sulphide of 

 manganese, is inferred from the appearances observed. 



Recrystallization of Deformed Iron.* — C. Chappell describes and 

 discusses the changes of structure, in relation to temperature, which occur 

 when cold-worked iron and steel are heated. In uniformly deformed 

 specimens no change takes place in the external boundaries of deformed 

 ferrite crystals up to about 500° C. At about 350° C, however, changes 

 begin to occur within the crystals. Rough granular markings in the 

 etched crystals, frequently in the form of parallel bands, appear to be 

 regions in which disintegration and incipient recrystallization of the 

 deformed ferrite crystals have taken place. These markings indicate the 

 recrystallization of the very severely deformed ferrite existing on and 

 about the planes along which deformation of the crystal had taken place 

 during cold-working. The disintegration of the crystals develops with 

 rise of temperature until at about 500° C. many of the crystals present 

 a completely granular appearance. AVith further rise of temperature, 

 minute independent crystals appear in the disintegrated regions ; these 

 crystals grow with great rapidity. At about 570° C. the crystal debris is 

 wholly replaced by the new crystals. From 570° to 700° C. these 

 crystals steadily increase in size ; above 700° C. further growth is very 

 slow, until complete recrystallization occurs at Ac 3 . Numerous experi- 

 ments were made on the recrystallization on heating of locally de- 

 formed specimens, in which the degree of deformation varied from point 

 to point. The gross crystallization occurring under certain conditions, 

 in such specimens, is described and explained. It is suggested that the 

 growth of crystals on annealing takes place by the sudden combination 

 into one crvstal of two or more contiguous crvstals, and not by the gradual 

 absorption by a large crystal of the smaller crystals surrounding it. The 

 process of recrystallization of deformed ferrite crystals is one of refine- 

 ment followed by growth. The extent to which refinement takes place 

 increases proportionately with the degree of plastic deformation. The 

 ultimate crystal size after annealing deformed iron may be regarded as 

 the resultant of these two opposing tendencies, and increases regularly 

 with decrease in the degree of deformation. The temperature of crystal- 

 lization becomes lower with increase in the degree of deformation. 



National Physical Laboratory. — A Leitzf Metallograph has been 

 installed, and. has proved useful for rapid work. Two metallurgical 

 Microscopes have been mounted on hinged supports, over openings in 

 the table. By a single movement of the hand, the Microscope can be 

 pushed into a receptacle, formed by a large bellows, beneath the table ; 

 the opening being then covered, the table is clear, and the Micro- 

 scope completely protected. The progress made in various researches is 

 indicated in the report. 



* Journ. Iron and Steel Inst., lxxxix. (1914, 1) pp. 460-502 (25 figs.), 

 t Nat. Phys. Lab. Annual Report, 1913-14. 



