ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 741 



The authors point out that the micrographical study of alloys 1ms 

 become a branch of physical chemistry. The subject is dealt with under 

 the following headings : 



1. Technique of Metallography. — The progress made by Le Chatelier 

 and others is indicated. 



2. Equilibrium Curves. — The earlier paper includes an account of 

 Heycock and Neville's well known work on the complex copper-tin 

 system. The iron-carbon system is considered somewhat fully in both 

 papers. In the second the valuable researches carried out in the 

 laboratory of G. Tammann are summarised. The constituents of iron- 

 carbon alloys are defined, and the conditions necessary to produce them 

 stated. 



3. Modifications of One Isolated Phase or of a Complex of Phases 

 within their Regions. — Thermal and mechanical treatments. This section 

 deals chiefly with researches on modes of deformation of metals. 



It is here only possible to give a very imperfect account of these 

 papers. As a guide to the literature of metallography of the last six 

 years they should be of great value to the student. They derive addi- 

 tional importance from the fact that one of the authors is the foremost 

 authority on the subject. 



Quaternary Steels.* — L. Guillet gives in detail the results of ex- 

 tensive researches on alloys containing iron, carbon, and two other 

 elements (nickel, manganese, chromium, vanadium, etc.) ; 250 alloys 

 were examined, micrographically and mechanically, following the author's 

 usual plan. The Guillery machine was employed for the shock tests. 

 The steels are classified according to microstructure, and the mechanical 

 qualities corresponding to each type of structure are indicated. The 

 effect of heat treatment (quenching, etc.) on steels of each class is stated. 

 Certain structures indicate the presence of certain elements, e.g. graphite 

 usually demonstrates the presence of silicon in fairly high proportion. 

 The structure may be simple, only one constituent being present, or 

 complex, with two or more constituents. Martensite and y-iron are the 

 simple structures. Nickel, manganese, chromium, tungsten, and molyb- 

 denum tend to convert pearlitic steels into martensitic, while vanadium, 

 silicon, and aluminium act in the opposite way. Martensitic steels, and 

 steels containing graphite, are useless in practice ; y-iron steels are 

 difficult to machine. For general purposes pearlitic steels are the only 

 useful class. 



Deformation and Fracture in Iron and Steel.j — By straining a 

 piece of ductile metal, one surface of which has previously been polished, 

 slip bands are developed on the polished surface. Controversy as to the 

 true nature of these slip bands has arisen. A method for studying their 

 configuration has been introduced by W. Rosenhain, who here gives 

 further details and numerous results obtained by its application. The 

 method is also adapted for examining the surface of fractures. The 

 specimen to be examined is imbedded in electro-copper. The composite 

 mass is cut through approximately at right angles to the surface to be 



* Journ. Iron and Steel Inst., lxx. (1906, 2) pp. 1-141 (145 figs.). 



t Tom. cit., pp. 189-228 (25 figs.). See also this Journal, 1905, p. 391. 



