ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 671 



to give results more definite than those obtained from cooling curves. 

 In alloys of nearly eutectic composition the separation of primary crystals 

 could hardly be detected by thermal methods, whilst the crystals were 

 clearly distinguished microscopically. The structure of most of the 

 sections was developed by etching and heat-tinting, followed by light 

 repolishing. 



Alloys of Iron with Arsenic and Bismuth.* — C. F. Burgess and 

 J. Aston have studied these alloys, prepared, free from carbon, from 

 electrolytic iron. The effect of arsenic in acid pickling baths in re- 

 tarding the rate of attack of the acid upon steel had suggested that 

 arsenic in steel might render it less readily corrodible. The author's 

 experiments did not bear out this notion, the iron-arsenic alloys resisting 

 corrosion little better than iron and steel containing no arsenic. The 

 addition of arsenic to iron improves its magnetic properties, but more 

 than 0"25 p.c. is detrimental in its physical effects. 



Some Iron-silicon-carbon Alloys.f — W. Gontermann has investi- 

 gated this ternary system within the limits Fe-Fe ? C-FeSi by the 

 method of thermal analysis, and has also revised the equilibrium diagrams 

 for the iron-carbon and iron-silicon systems. It is suggested that the 

 formation of " kish " in the high-carbon alloys of the iron-carbon system 

 may be explained by the decomposition of cementite on melting into 

 two immiscible liquids, one considerably richer in carbon than the other. 

 The equilibrium diagram of the ternary system, given and explained by 

 the author, does not permit of a brief summary. Typical photomicro- 

 graphs are given. 



Special Steels.J — L. Griiillet indicates the directions in which progress 

 has been made in the manufacture of alloy steels since the Brussels 

 Congress. While the polyhedric steels are losing in importance, pearlitic 

 special steels are receiving wider application^ In their manufacture the 

 objects aimed at are (1) increase in mechanical strength ; (2) simplifica- 

 tion of thermal treatment ; (3) for parts exposed to friction, increase in 

 resistance to abrasion. 



Heat-treatment of Spring Steel. || — L. H. Fry has determined the 

 transverse elastic limit and modulus of elasticity of steel containing 

 L* 01 p.c. carbon. - 38 p.c. manganese, heat-treated in various ways. 

 The modulus of elasticity was found to be practically constant and in- 

 dependent of the heat-treatment, its value being 29 - 30 x LO 6 lb. per 

 square inch. 



"Slag Enclosures" in 15teel.1T — W. Rosenhain calls attention to 

 the possible effect upon the strength of steel of those non-metallic 

 bodies which may be designated as "slag enclosures." A number of 

 photomicrographs of typical forms of these enclosures are given. The 



* Electrochem. and Met. Ind., vii. (1909) p. 276. 

 t Zeitschr. Anorg. Chem., lix. (1908) pp. 373-413 (15 figs). 

 X Proc. Int. Assoc, for Testing Materials No. 5 (1909) 7 pp. 

 § See this Journal, 1909, p. 538. 



|| Proc. Int. Assoc, for Testing Materials, No. 5 (1909) 9 pp. (2 figs.). 

 1 Op. cit., No. 10, (1909) 10 pp. (7 figs.). 



