ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 109 



•alloy consisted of a single solid solution and had the usual polygonal 

 structure. Twinning was evident in the alloys rich in cobalt but was not 

 observed in the nickel-rich alloys. Nickel oxide is soluble in molten 

 nickel and the eutectic formed on solidification has a well defined 

 structure. 



Lead-tin-antimony Alloys.*— W. Campbell discusses the equilibrium 

 of this ternary system, and gives a number of photomicrographs. In 

 many cases the observed structure is riot in full agreement with the 

 equilibrium diagram, owing to the failure of the alloy to attain 

 equilibrium during solidification and cooling. 



Porous Metals.f — If an alloy, which consists of primary crystals 

 together with a eutectic, be heated just above the melting-point of the 

 eutectic, the liquid eutectic may be extracted by means of a centrifuge, 

 or by forcing another liquid in under pressure. The specimen thus 

 obtained possesses its original form, but consists of the primary crystals 

 with microscopic spaces between. H. I. Hannover describes the pro- 

 cess, giving details of the precautions necessary. Porous lead and 

 porous antimony may be obtained from lead-antimony alloys containing 

 excess of lead in one case, excess of antimony in the other case. Porous 

 lead finds an application as accumulator plates ; porous bearings may 

 receive a constant supply of lubricating oil through the pores. 



Coalescence in Lead. J— Coalescence, the growth of certain crystals 

 by absorption of surrounding crystals, occurs in rolled lead at ordinary 

 temperatures. H. Baucke shows that this growth is accelerated during 

 immersion in a suitable electrolyte. Dilute etching reagents, such as 

 5 p.c. acetic acid, and 5 p.c. nitric acid in alcohol, have been found to 

 act in this manner on lead. The growth is rapid in lead foil, but less 

 evident in plates. Local coalescence in a specimen of lead has been 

 observed to be followed by rapid corrosion of the same region. It has 

 not been found possible to control the rate and degree of coalescence 

 caused by immersion in an electrolyte. 



Growth of Crystals in the Annealing of Cold-worked Metals. § 

 By annealing cold-rolled sheets of tin, lead, zinc, aluminium, copper, 

 and iron at different temperatures, F. Eobin has shown that, though the 

 size of the resulting crystals depends upon the temperature and length 

 of time of annealing, the size of crystal is not directly proportional to 

 the temperature for a given duration of annealing. Experiments on 

 the same metals have shown that when locally deformed specimens are 

 annealed, the crystals in the most strongly deformed parts do not show 

 abnormal growth, but the distorted crystals at the edge of the region of 

 deformation grow enormously at the expense of the contiguous unde- 

 formed crystals. 



* Metallurgie, ix. (1912) pp. 422-5 (15 figs.). 



t Rev. Metallurgie, ix. (1912) pp. 641-6 (7 figs.). 



i Int. Zeitschr. MetaUographie, ii. (1912) pp. 243-57 (15 figs.). 



§ Comptes Rendus, civ. (1912) pp. 585-7, 716-8. 



