ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 757 



Some Phenomena of Permanent Deformation in Metals.* — G. H. 

 Gulliver corrects his earlier liypotliesis that the " contractile cross " is 

 the result of the slipping of crystalline grains over each other. By 

 subjecting thin strips of aluminium — rendered coarsely crystalline by 

 heating nearly to melting point — to tension, and watching the progress 

 of deformation by the Microscope, the author has found that (1) the 

 phenomena of constriction and fracture are due to excessive local 

 " slipband " deformation ; (2) the contractile cross passes through the 

 crystalline grains ; it is somewhat influenced by the degree of coarseness 

 of the crystalline structure, but is independent of the directions of the 

 boundaries of the crystalline grains. 



Passage from the Liquid to the Solid State.f — ■ Three papers J 

 by G. CarUrad are here reprinted, together with a series of remarkable 

 photomicrographs and a necessarily incomplete account by F. Osmond 

 of the further researches of Cartaud interrupted by his death. Indica- 

 tions of a cellular, as distinct from a crystalline structure, are obtained 

 when lead, tin, zinc, and other metals are cast on a sloping sheet of 

 glass. In this manner a thin and rapidly solidified layer of the metal 

 is formed. There appears to be some relation between the cellular 

 network and the crystalline structure. Cartaud applied the term 

 " metalloblast " to the primitive cellule, " crystalloblast " to the incipient 

 crystal. It is suggested that metals, during solidification, pass through 

 the cellular state before becoming truly crystalline. Osmond considers 

 this subject to be a fruitful field for research. 



Hardness of Tool Steels. § — Demozay gives the results of deter- 

 minations of hardness by the Brinell method of tool steels, some being- 

 high-speed steels containing chromium and tungsten, hardened at 

 different temperatures in air, oil, or water. Similar measurements were 

 made at 100° C, 250° C, 400° C, and 500° C, on the steels after 

 difi'erent previous treatments. For the high-speed steels the hardness 

 rises to a maximum at 200-250° C, slowly decreasing as the tempera- 

 ture is further raised. For certain steels the temperature of maximum 

 hardness is higher as the quenching temperature is higher. 



Phenomena of Solidification and of Transformation in Alloys. || — 

 A. Portevin works out afresh the application of the phase rule to the 

 equilibrium of a two-component system. The departure from stable 

 equilibrium, produced by insufficiently slow cooling, and resulting in a 

 condition of labile equilibrium, which occurs so frequently in alloys 

 having transformation points in the solid state, is fully considered. 



Specific Heat of Iron.!— P. Oberhoffer lias made very careful de- 

 terminations of the mean specific heat of iron between 0° C. and 

 temperatures from 265-1528° C. A full account is first given of 

 previous work. Objections which can be urged against the methods of 



* Proc. Inst. Mech. Engineers, 1907, ii. pp. 519-24 (9 figs.). 



t Rev. de M6tallurgie, iv. (1907) pp. 819-32 (72 figs.). 



t Comptes Rendus, 1901, 3903, and 1904. 



§ Rev. de M6tallurgie, iv. (1907) pp. 885-900 (11 figs.). 



II Tom. cit., pp. 915-25 ( 5 figs.). 



«t Metallurgie, iv. (1907) pp. 427-43, 447-55 and 486-97 (22 figs.). 



