ZOOLOGY AND BOTANY, MICROSCOPY, ETC. f>35 



nickel. Samples of steel containing np to 30 p.c. cobalt with ' 8 p.c. 

 carbon, were examined and found to be pearlitic without exception. As 

 the percentage of cobalt increases, the breaking load and elastic limit 

 are gradually raised, with a corresponding reduction in elongation and 

 contraction of area ; no abrupt change in mechanical properties occurs. 

 Cobalt steels have no industrial application. 



Classification of Ternary Steels.* — L. Guillet recapitulates the 

 results he has obtained in the course of his extensive investigations on 

 alloys of iron and carbon with a third element, and draws some general 

 conclusions. The method adopted was to examine, micrographically 

 and mechanically, two series of alloys in each group, containing re- 

 spectively 0*2 p.c. and 0'8 p.c. carbon, the percentage of the third 

 element gradually being increased. The elements, the effects of which 

 upon steel the author has thus demonstrated, are nickel, manganese, 

 chromium, tungsten, molybdenum, vanadium, silicon, aluminium, cobalt, 

 tin, and titanium. The steels are classified according to the results of 

 microscopical examination as — (1) pearlitic ; (2) martensitic ; (3) con- 

 taining y iron ; (4) containing a carbide ; (5) containing graphite. 



The influence of the third element upon the mechanical properties of 

 the steel is shown in a series of curves, in which the abscissae are per- 

 centages of the element, and the ordinates represent the differences 

 between the properties of the alloy and those of carbon steel containing 

 the same percentage of carbon. Diagrams of this kind are given for 

 maximum tensile stress, elongation, and brittleness. The correspondence 

 between micro-structure and mechanical properties is thus strikingly 

 demonstrated. The author proposes to take up the investigation of 

 quaternary alloys, such as nickel-manganese, nickel-chromium, and 

 nickel- vanadium steel. 



Metallography Applied to Foundry Work.f — In an article 

 advocating the use of the Microscope in foundry work, A. Sauveur 

 points out that the information as to the chemical composition and 

 physical properties of metals obtained by an inspection of fractures, a 

 method which has been universally employed in the foundry, may be 

 largely supplemented by microscopical examination of polished and 

 etched sections. Chemical analysis, again, while furnishing the nltimate 

 composition of the metal, fails to suggest its proximate analysis; 

 valuable information as to this proximate analysis may be obtained by 

 the use of the Microscope. The author describes the methods which he 

 has found to be most satisfactory for the preparation of the surfaces of 

 sections. 



Scientific Development of the Art of Polishing.^— In the course 

 of a lengthy article on this subject, P. Osmond and <!. Cartaud show- 

 how the preparation of metallic surfaces for microscopical examination 

 may affect the results obtained. The operation of polishing consist m 

 the removal of metal from the surface, by means of a Hie, emery, or 



* Rev. Metallurgie, ii. (1905) pp. 350-67 (13 figs.), 

 t Iron and Steel Mag.,ix. (1905) pp. 547-53(1 fig.). 



X Rev. Gen. des Sci., xyi.(1905) pp. 51-65(46 figs). See alao Lug. -Mag., xxx.x. 

 (1905; pp. 261-3. 



