ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 383 



dealt with either by reducing its amount or by raising the position of 

 the segregate. The degree of segregation is lessened by addition of 

 akiminium to the molten steel and by hastening solidification. 



Chromium-Tungsten Steels. — L. Guillet* has examined micro- 

 scopically 24: steels containing carbon • 14-0 * 84, chromium • 7-21, and 

 tungsten 2-20 p.c, after different heat treatment. Among the author's 

 conclusions are : (1) the constituents present in the normal steel are 

 pearlite, martensite, and a triple carbide of iron, chromium and tungsten, 

 accompanied by martensite, sorbite (or troostite) or y-iron ; (2) the most 

 frequently observed structure of the normal steels resembles that of 

 high speed tool steels — grains of carbide in a matrix of troostite or 

 sorbite. The mechanical properties on the whole are such as might be 

 expected from the micro-constitution and from the author's previous 

 results on chromium steels and tungsten steels. The effect of quenching 

 at different temperatures and the bearing of the numerous facts observed 

 on high-speed steels, are discussed at some length. In the steels con- 

 taining carbide that constituent could be caused to disappear by heating 

 at 1200° C. for a sufficiently long time ; on quenching, an extremely fine 

 martensite resulted. 



Alloys of Manganese and Copper.— S. Wologdinef has determined 

 the freezing point curve and investigated the microstructure and 

 hardness of a series of manganese-copper alloys. The melting point of 

 manganese was found to be 1275° C. The alloys are classified in three 

 groups — (1) 0-40 p.c. manganese, apparently solid solutions of manganese 

 in copper ; (2) 40-78 p.c. manganese, very hard and brittle, containing 

 two constituents ; (:•)) 78-100 p.c. manganese, also hard and brittle and 

 falling to powder in air. The most satisfactory etching reagents were a 

 very dilute solution of ammonium sulphide in water, boiling water (which 

 attacks manganese), and for the groups (2) and (8) iodine solution. A 

 maximum in the freezing point curve at 1140° C.and 78 p.c. manganese 

 is ascribed to the compound MUiCu. Two minima exist, at 40 p.c. 

 (850° G.) and 89 p.c. manganese (1005° C). The latter is a eutectic 

 point. Hardness was measured by the Brinell method. 



Metal-testing Laboratory.^ — L. Guillet describes the equipment of 

 the temporary laboratory fitted up at Brussels for the Congress of the 

 International Association for Testing Materials, in which were given 

 demonstrations of modern metliuds of testing. The tests were made 

 with great rapidity and considerable accuracy, and comprised — (1) Pre- 

 paration of polished and etched sections and of photomicrographs of 

 these ; (2) critical point determinations by the Saladin method ; (3) 

 shock tests on notched bars in the Guillery machine ; (4) Brinell hard- 

 ness measurements ; and (5) shearing tests by Fremont's method. Thirty- 

 six samples were tested in the four days during which the laboratory was 

 working. The principal etching reagents used were picric acid for iron 

 alloys and ferric chloride in hydrochloric acid for alloys of copper. 



* Rev. Metallurgie, iv. (1907) pp. 5-24 (16 figs.). 

 t Tom. cit., pp. 25-38 (13 figs.). 

 X Tom. cit,, pp. 189-200 (10 figs.). 



