ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 263 



respectively. The manganese sulphide and slag occurred as strings or 

 veins in (b), but were evenly distributed as small globules in (a). Heat- 

 ing a little above Ac 2 - 3 completely refined the structure of (a), but 

 did not altogether remove the ferrite network of (&). A network of 

 manganese sulphide or slag appears to prevent complete refining by 

 acting as nuclei on which the ferrite precipitates. 



Defects in Steel Rails. — H. Fay and E. W. G. Wint* describe the 

 various ways in which the presence of slag (manganese sulphide, 

 manganese silicate, and possibly other substances) may cause the failure 

 of rails. In many sections examined the sulphide was seen to be broken 

 at right angles to its length, its extreme brittleness causing it to break 

 during preparation for microscopic examination. Cracks invariably begin 

 in and follow from one slag area to another. Flow of metal in many 

 cases appears to be due to the presence of internal cracks originating in 

 slag inclusions. Hard spots in rails are due to (1) imperfect solution of 

 f erro-manganese ; (2) surface hardening through friction of the wheels ; 

 (3) segregation. The authors believe that some hard areas containing 

 martensite and troostite, found in a nickel steel rail, were caused by segre- 

 gation of nickel. 



R. Jobf has investigated some defective open-hearth steel rails, 

 and has found that failure was the result of segregation, piping, and 

 unsoundness. 



P. H. Dudley % has found that in numerous cases of splitting of 

 heads of rails, etched sections of the rail show dark streaks, found to 

 be harder and to have a higher carbon content than the rest of the 

 rail. The presence of these dark streaks is ascribed to the inclusion in 

 the steel of metal washed away from the cast-iron base of the ingot 

 mould, by the impinging of the stream of molten metal when the ingot 

 was cast. 



Tests of Ingots.§ — J. E. Howard has examined with the unaided 

 eye and microscopically, sections of ingots, and of the various forms 

 derived from them during their manufacture into rails. In this way 

 the effect of reduction by rolling upon size and shape of grain, gas or 

 shrinkage cavities, and slag inclusions, was followed step by step. 



Closing of Blowholes in Steel Ingots.|| — H. M. Howe found that, 

 while comparatively great variations in density occurred in a steel 

 ingot due to the presence of blowholes, the plates rolled from the same 

 ingot were of uniformly high density. Contrary to the generally 

 accepted view, it would appear that the gas is driven out of the blow- 

 holes during rolling. It should, therefore, be possible to close and weld 

 up blowholes by rolling. 



Structure of Cast Iron.^f — F. J. Cook and G. Hailstone explain 

 variations occurring in the mechanical properties of a series of cast irons 

 of identical chemical composition, by differences which they found in 



* Amer. Soc. for Testing Materials, Prcc. ix. (1909) pp. 77-89 (14 figs.). 

 t Tom. cit., pp 90-97 (12 figs.). % Tom. cit., pp. 98-105 (9 figs.). 



§ Tom. cit., pp. 319-26 (10 figs.). || Tom. cit., pp. 327-47 (7 figs.). 



% Foundry, xxxv. (1909) pp. 21-3 (13 figs.). 



