ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 715 



"Filiations" of Metallic Alloys.* — The heterogeneous mass 

 obtained by the superposition of two molten metals, in such a manner 

 that mixing is incomplete, is termed by Le Gris a " filiation " of a 

 metallic alloy. A successful preparation contains one metal in a pure 

 state at the bottom, the other pure metal at the top, while the inter- 

 mediate layers represent, in order, every possible composition of binary 

 alloy. Le Gris has so improved the method, originally introduced by 

 Le Chatelier, that a complete " filiation " can be obtained not exceeding 

 1 mm. in height. These small preparations are made by bringing into 

 contact fragments of the two metals, melted and in the globular state, 

 and cooling rapidly the single globule formed. Larger "filiations" 

 are made in crucibles. The preparations are useful for a rapid study of 

 the metallography of the complete system, and by successive re-polishings 

 and etchings with different reagents it is a simple matter to ascertain 

 which reagent is the most suitable for the identification of any one con- 

 stituent. Similar in principle is a method described for the study of 

 the effect of speed of cooling upon grain-size and other structural 

 features. A small ingot is cast in a non-conducting mould, which has 

 a large cold block of metal as its base. The bottom of the ingot is thus 

 rapidly chilled and solidified, while the rate of cooling becomes slower 

 as the top of the ingot is approached. 



The author determines the hardness of the various constituents found 

 in a " filiation " by a modification of the Brinell method. The end of a 

 drawn thread of glass is melted, so that a ball having a diameter of a 

 fraction of a millimetre is formed. A series of impressions is made, 

 proceeding from one end of the preparation to the other, with a load of 

 a few hundred grams ; the impressions are conveniently measured on a 

 photomicrograph. The presence of impurities in one of the metals 

 usually has a marked effect upon the microstructure of a " filiation " ; 

 this observation may be utilized for the detection of impurities and an 

 approximate determination of the amount present. A " filiation " may 

 be prepared and microscopically examined in a quarter of an hour. 



Jointed Arm for Workshop Microscope. f—S. Prauss describes a 

 useful modification of the Stead Workshop Microscope. The Micro- 

 scope is carried by a jointed arm, the other end of which is attached to 

 the specimen by a vice or an electro-magnet. Any surface of a large 

 mass of metal may thus be examined. 



Corrosion of Metals. J — G. D. Bengough reviews generally the present 

 knowledge of the corrosion of non-ferrous metals. The literature of the 

 subject is summarized, and the electrolytic theory of corrosion, to which 

 the author attaches much importance, is clearly explained. The problems 

 awaiting solution are stated, and a scheme for the investigation of the 

 corrosion of 70 :30 brass, in the form of condenser tubes, is put forward. 



J. T. Corner § describes some cases of corrosion of metals and alloys. 



* Rev. Metallurgie, viii. (1911) pp. 613-25 (21 figs.). 

 t Metallurgie, viii. (1911) pp. 121-6 (6 figs.). 



I Journ. Inst. Metals, v. (1911) pp. 28-114 (4 figs.). Report to the Corrosion 

 Committee of the Institute of Metals. 



§ Journ. Inst. Metals, v. (1911) pp. 115-26. 



