ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 435 



Magnesium-aluminium-zinc Alloys.*— G. Eger, in the course of a 

 lengthy report upon the constitution of the ternary magnesium-aluminium- 

 zinc alloys, describes the microstructure of a considerable number of them. 

 Marked brittleness rendered the polishing of many of the specimens very 

 difficult. The presence of hard crystalline compounds frequently caused 

 the structure to be sufficiently revealed by simple polishing. 



Ancient Iron Objects. f — H. Hanemann describes the microstruc- 

 ture of some Celtic iron articles probably not less than 2000 years old, 

 found in excavations near Romhild. A pointed tool, the form of which 

 suggested that it had been attached to a wooden handle, was coated with 

 rust to a depth of about 1 mm. The rear part was found to consist of 

 ferrite and pearlite with which much slag was intermingled. The Wid- 

 mannstatten structure indicated a high forging temperature. The point 

 beneath the rust was hard to the file. A transverse section was found 

 to consist of martensite to a depth of about 1 mm. Below this was 

 martensite containing small patches of osmondite. The structure of 

 this tool, which must have been quenched in water and not tempered, 

 demonstrates the great antiquity of the process of hardening steel, and 

 also indicates that martensite, which is understood to be a metastable 

 constituent, may persist practically unchanged throughout long periods 

 at ordinary temperatures. An axe was found to consist of ferrite with 

 included slag. Etching with hydrochloric or nitric acid developed a net- 

 work of shadowy lines which had no apparent relation to the crystalline 

 structure of the ferrite. A ring had the structure of unhardened steel. 

 The remaining Celtic objects consisted of ferrite with included slag. 

 An ancient Greek object — a small figure of a faun — consisted of graphite, 

 pearlite, ferrite, and the ternary phosphoric eutectic, and had apparently 

 been gilded. Its cast-iron structure suggested that cast-iron was known 

 to the ancient Greeks. 



Ternary Alloys of Iron-nickel-manganese, Nickel-manganese- 

 copper, and Iron-manganese-copper.|— N. Parravano, in working out 

 the equilibrium diagrams, has studied the microstructure of the ternary 

 alloys. In the copper-iron-manganese system the limits of solid solu- 

 bility were determined by microscopic examination of specimens which 

 had undergone prolonged annealing. Etching reagents used were a solu- 

 tion of ferric chloride in dilute hydrochloric acid, a mixture of ammonia 

 and hydrogen peroxide, dilute nitric acid, and picric acid in alcohol. 

 In many of the alloys the solid solution crystals had a cored structure. 



Constitution of Carbon-molybdenum Steels. § — T. Swinden reports 

 the results of a further lengthy investigation of the properties of a series 

 of carbon-molybdenum steels, and includes a description of the micro- 

 structure of specimens (1) quenched from 800° C. ; (2) quenched from 



* Int. Zeitschr. Metallographie, iv. (1913) pp. 29 128 (58 figs.), 

 t Int. Zeitschr. Metallographie, iv. (1913) pp. 248-56 (10 figs.), 

 j Int. Zeitschr. Metallographie, iv. (1913) pp. 171-202 (61 figs.). 

 § Iron and Steel Inst. Carnegie Scholarship Memoirs, v. (1913) pp. 100-168 

 (50 figs.). 



