220 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



tory explanation of the so-called Widmannstattian figures 

 until our knowledge of the effect of a minute quantity of for- 

 eign substances in iron is better understood than now, a sub- 

 ject which investigators in both pure and technical chemistry 

 are now studying with great interest, in order to discover 

 how far those substances, usually called impurities in iron, 

 are to be regarded as hurtful. Very small proportions of 

 these supposed impurities often introduce important modifi- 

 cations in the nature of the iron. For instance, one per cent., 

 or less, of phosphorus so far modifies cast iron that it will re- 

 sist the action of concentrated sulphuric acid to a greater de- 

 gree than when entirely free from phosphorus ; and those who 

 separate silver and gold by the sulphuric- acid process find 

 that some cast-iron vessels are destroyed in a few weeks, 

 while others will last for years. Phosphorus also modifies 

 the physical properties, imparting to the iron more fluidity 

 when in a melted state, and furnishing more compact cast- 

 ings. In regard to the Widmannstattian figures, he states 

 that it is his belief that in the crystallization of iron, as in 

 the crystallization of all other substances containing impuri- 

 ties, there is a tendency to eliminate the foreign constituents 

 to the exterior portion of the crystals, and it is between the 

 crystals, and contiguous to their surfaces, that we find the 

 greater part of the foreign constituents mixed with more or 

 less of the predominating materials. In meteoric iron, which 

 always contains phosphorus, it may be safely premised that 

 if the iron pass slowly into the solid condition, and is there- 

 fore allowed to crystallize more or less perfectly, we may ex- 

 pect, in certain parts of the mass representing the spaces be- 

 tween the crystals, to find a more or less perfect elimination 

 of the phosphorus, thus destroying the homogeneous charac- 

 ter of the mass, and rendering its different parts variously 

 susceptible to the action of chemical agents, and so pro- 

 ducing that mottled surface known as the Widmannstattian 

 figures. 4 D, 1874, 392. 



A BISMUTH MINE IN FRANCE. 



For two or three years past a bismuth mine has been work- 

 ed at Meymac (Correze), in Central France. The vein occurs 

 in one of the ramifications of the granitic chains separating 

 the basins of the Vienne and the Creuse from that of the Dor- 



