390 Intelligence and Miscellaneous Articles, 



longs to the rhombohedral system, because it comes within the class 

 of perfectly brittle metals, the crystalline forms of which, as far as 

 we are acquainted with them, are rhombohedral. 



But the difference between malleable and cast iron does not con- 

 sist merely in the crystalline structure, which may be open to doubt, 

 but likewise in the physical characters, and to some extent in the 

 chemical behaviour, for instance the cohesion, hardness, resistance 

 to fracture, fusibility, oxidizability, solubility in acids, &c. He is 

 of opinion that these circumstances alone'would justify the inference 

 that there is a specific difference between malleable and cast iron, 

 which he compares with those presented by the modifications of 

 sulphur, phosphorus, arsenious acid, by glass and Reaumur's porce- 

 lain. 



Finally, with regard to steel, Fuchs is of opinion that it is an 

 alloy of tesseral and rhombohedral iron. The per-centage of carbon 

 which it contains varies from 0*625 (Gay-Lussac) to 1*9 (Karsten). 

 It cannot therefore be regarded as a definite and constant compound. 

 It differs from other alloys in the circumstance that its character^ 

 may suffer considerable alteration without an accompanying addition 

 or loss of substance, as in the hardening and softening of steel, 

 changes which Fuchs supposes to be the result of an internal and 

 alternating metamorphosis, by which the relative proportion of the 

 two species of iron is altered. Thus, according to his views, in 

 hardened steel the rhombohedral preponderates over the tesseral 

 iron, and the reverse in soft steel. Very hard steel would, therefore, 

 from the very small proportion of tesseral iron, approximate closely 

 to cast iron ; and this conjecture is favoured by the low specific 

 gravity of hardened steel. By the process of tempering, the pro- 

 portion of tesseral iron in steel would increase with the temperature. 

 The two kinds of iron in steel may be regarded as in a state of con- 

 stant mutual tension, which may perhaps be the reason why steel 

 retains permanently communicated magnetism, \;hile malleable iron 

 does not. 



An experiment of Schafhautl's* would appear to favour the 

 above views. He submitted a piece of a razor-blade to the action 

 of tolerably strong hydrochloric acid for several days, at the end of 

 which time it was found to have been very unequally attacked. 

 When washed, dried and broken in a mortar, it furnished fragments, 

 some of which could be powdered, while others were malleable. 



With regard to the important and much-discussed question of the 

 alteration of malleable iron when exposed to continuous vibration, 

 concussion or torsion, in consequence of which it acquires a granular 

 fracture, Fuchs admits that such an alteration takes place even in 

 the best-worked metal, but does not altogether agree with the ex- 

 planation usually offered for it, viz. the gradual assumption of a cry- 

 stalline texture ; and is of opinion that it consists in the passage of 

 the iron from a fibrous crystalline state to a granular crystalline 

 state, a change in the aggregation, not an essential metamorphosis. 

 When iron passes from the fibrous into the granular texture, the 

 cohesion of the molecules is lessened ; and by their aggregation into 



* PrechtPs Technologischer Enq^clopiidie, Abhandlung uber den Siahl, 

 Tol. 3nr. p. 377. 



