472 SUMMARY OF CURRENT RESEARCHES. 



Austenite may be distinguished from martensite by immersing the 

 metal in a solution of ammonium chloride (a 10 p.c. solution for in- 

 stance), while it is connected with the positive pole of a bichromate 

 cell, the negative pole consisting of a piece of platinum foil, or of lead, 

 or of iron foil. The specimen is examined every ten seconds until the 

 etching is sufficiently deep. A very dilute solution of hydrochloric 

 acid may also be used, but the use of a battery is always desirable, as 

 it increases the regularity of the chemical action. In both cases 

 martensite is first coloured, successively yellow, brown, and black. 



Micro-structure i of Steel Quenched from the Melting-Point. * — 

 Mr. P. C. Lan has obtained two excellent photographs very clearly 

 illustrative of steel structure ; the martensite is in large masses and 

 visible by low magnification. A third photograph shows the remarkable 

 change in structure due to presence of tungsten. 



Bibliography. 



Behbens, H. — Mikrochemische Technik. 



2nd ed., Hamburg (Voss), 1900, 8vo, 68 pp. 

 Bohm, A., u. A. Oppel — Taschenbuch der Mikroskopischen Technik. (Pocket- 

 book of Microscopical Tecbnique.) 



4th ed., Munich (Oldenbourg), 1900, 8vo, 240 pp. 



Eberth, C. J. — Friedlander's Mikroskopische Technik zum Gebrauche bei medi- 

 cinischen und pathologisch-anatomischen Untersuchungen. ( Friedlander's Micro- 

 scopical Technique for use in Medicinal and Pathological -anatomical Inquiries.) 



Berlin (Kronfeld), 1900, Svo, 359 pp. and 86 figs. 



L em berg, J. — Zur Mikrochemischen Untersuchung einiger Mineralien. (On the 

 Microchemical Examination of certain Minerals.) 



Zeilschr. d. deutschen Geol. Ges., LII. (1900) pp. 48S-96. 



Lenhartz, H. — Mikroskopie und Chemie am Krankenbett. 'Clinical Microscopy 

 and Chemistry.) 



3rd ed., Berlin (Springer), 1900, Svo, 360 pp., 73 figs., and 3 pis. 



Meyer, A. — Lie [Grundlagen innd die Metboden fur die Mikroskopische Unter- 

 suchung von Pflanzenpulvern. (Elements and Methods of Microscopical Ex 

 animation of Plant Powders.) 



Jena (Fischer), 1901, Svo, 258 pp., 8 pis., and 18 figs. 



Kinke, F. — Das Mikroskop im Chemischen Laboratorium. (The Microscope in the 

 Chemical Laboratory.) Hanover (Janecke), 1900, Svo, 74 pp. and 202 figs. 



Stead, J. E. — Practical Metallography. 



[J. E. Stead considers that this may be studied under the following sections : — 

 (1) Preliminary preparations of the specimens. (2) Methods of polishing. 

 (3) Etching the specimens. (4) Mounting the specimens. (5) Neces- 

 sary Microscope accessories. (6) Photographing the developed structures. 

 (7) Lists of apparatus. The treatment of the subject under these heads 

 is expressly intended to help investigators ; and the author's advice, on 

 account of his eminence, is naturally of the greatest value to micro- 

 scopists who are interested in metallography.] 



Proc. Cleveland Institution of Engineers, Feb. 26, 1900; 

 and Metallographist, 1900, pp. 220-44 (8 figs.). 



* Metallographist, 1900, pp. 244-6 (3 figs.). 



