ZOOLOGY AND BOTANY, MICROSCOPY, ETC. L23 



than those of y- or a-iron. It is, therefore, improbable that the martensite 

 needles can be merely a mixture of a- and y-iron. 



Transformations of Iron and Steel.*— Grenet holds that the trans- 

 formation of iron, and the solution of carbon in iron, are not two 

 separate and distinct phenomena. When carbide of iron goes into 

 solution in iron, the iron changes from the a to the y condition. The 

 case of pure iron undergoing the change from a to y is the limiting 

 case, the concentration of carbon in the y solid solution formed being' 

 nil. Assuming the stability of cementite, the only phases occurring in the 

 iron carbon system in the temperature range -180° C. to +1200° C, 

 and the concentration range to 1 • 60 p.c. carbon, are f errite, cementite, 

 and solid solution. . 



Hardness of Steel.f — Grenet has sought to determine if the effect 

 of annealing quenched or cold worked steel reaches a limit for any 

 given temperature. Small pieces of a hard carbon steel and a nickel 

 chromium steel were quenched in water from 800° C. and heated for 

 various lengths of time, up to 04 hours, at 30o°, 500°, 650°, and 675° C. 

 Hardness was determined by the Brinell method. The annealing effect 

 at 300° C. was practically complete after 15 minutes. At 500°, 650° 

 and 675° C, the effect was not complete after It! hours, though after 

 four hours the action was very slow. Variation in temperature of 

 annealing has a relatively much greater effect than variation in length 

 of time. 



Use of Metallic Deposits in Metallography.! — F. Giolitti has 

 applied the method of depositing thin layers of metal on the polished 

 surface of an alloy by immersion in a solution of a metallic salt, to the 

 study of solid solutions. Indications of the heterogeneity of solid 

 solutions may thus be obtained. The method has been employed in 

 the study of bronzes. 



Rate of Change in Alloys. §— G. 1). Bengough describes a method 

 of determining the rate of change in metastable solid alloys when heated. 

 Portions of the alloy are heated at a selected temperature for various 

 lengths of time, and quenched in water. Photomicrographs are taken 

 and enlargements on bromide paper are made. The relative proportions 

 of the phases present are determined by cutting them out and weighing 

 the paper. 



Surface-flow in Calcite.|| — By a development of the method of 

 step-by-step etching, G. T. Beilbyhas shown that the disturbance of the 

 surface of calcite by polishing penetrates to a depth of 500 to 1000 /*/*. 

 The method of etching consists in placing on the polished surface a drop 

 of water containing a minute and known quantity of hydrochloric acid. 

 A known quantity of calcium-carbonate is thus dissolved, and the depth 

 removed by a number of successive etchings is calculated. By illuminat- 

 ing by the nearly critical image of the sun, the author detected a roughen- 



* Bull. Soc. Chim.,v. (1909) pp. 758-64 (4 figs.). 

 + Rev. Metallurgie, vi. (1909) pp. 1054-9 (3 figs.). 



t Gaz. Chim. Ital., xxxviii. (1908) pp. 3o2-7, through Journ. Chem. Soc, xciv. 

 (1908) pt. 2, p. 945. § Journ. Soc. Chem. Ind., xxvii. (1908) pp. 752-3. 



|| Proc. Roy. Soc, Series A, lxxxii (1909) pp. 599-605. 



