ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 405 



Simple Apparatus for Micrography.* — Gr. Revol describes an inex- 

 pensive Microscope suitable for the examination of metal surfaces in 

 the workshop. 



Alloys of Iron with Sulphur/f — Ziegler gives a lengthy descrip- 

 tion of the microstructure of iron-sulphur alloys containing 0-30 p.c. 

 sulphur, and also of alloys containing varying amounts of carbon, 

 manganese, etc., in addition to the sulphur. In the iron-sulphur 

 system two constituents only were observed, ferrite, and the eutectic 

 iron-sulphide of iron. The compound structure of the eutectic is 

 visible only when the alloy has been slowly cooled. Oxygen may be 

 present as an impurity in the eutectic. The addition of moderate 

 amounts of carbon to the alloy causes pearlite to appear, but does not 

 otherwise affect the structure. Troilite, the constituent containing the 

 sulphur in meteorites, appears to be a similar eutectic, but probably 

 contains some oxide in addition to the iron and sulphide of iron. The 

 structure of most of the alloys was visible after polishing, but was 

 more clearly revealed by etching with picric acid in alcohol, either a 

 5 p.c. or a saturated solution. 



Metallography of Quenched Steels4— C. Benedicks presents some 

 criticisms of the conclusions reached by Kourbatoff and by Maurer.§ 

 It is possible that austenite undergoing transformation into troostite 

 always passes through the martensite stage. The existence of a re- 

 versible transformation at 137° C, austenite ^ troostite, is not probable. 



National Physical Laboratory. — The annual report contains 

 much matter of interest. The following points in the report on the 

 metallurgical department may be noted. The great complexity of 

 the equilibrium diagram of the ternary system, copper-aluminium- 

 manganese, has necessitated the restriction of its investigation to the 

 region 0-10 p.c. manganese and 0-12 p.c. copper. A peculiarity, as 

 yet unexplained, has been noted in a small group of the alloys prepared. 

 The freezing-point of one of these alloys remelted several weeks after its 

 preparation is lower than that of the freshly-made alloy. An improve- 

 ment lias been effected in the ultra-violet photomicrographic apparatus 

 by the introduction of a " compensating lens " into the optical system 

 of the Microscope. If the image is visually in focus with blue lights 

 the compensating lens being used, the ultra-violet image is photo- 

 graphically in focus when the compensating lens is removed. Good 

 definition has been obtained in ultra-violet photomicrographs at 400 

 diameters, but serious obstacles, arising chiefly from internal reflections, 

 have been met at higher magnifications. 



A series of determinations of " temperature-density " curves has 

 been made. The work projected for the current year includes further 

 investigation of the alloys of copper and aluminium with manganese, 



* Rev. Me'tallurgie, iv. (1909) pp. 442-5 (3 figs.). 



t Tom. cvt., pp. 459-93 (22 figs.). 



t Tom. cit., pp. 494-501. 



§ See this Journal, 1908, pp. 783-4. 



|| Nat. Phys. Laboratory, Report for 1908. 



