354 Mr. Mallet on the Physical Conditions 



These mutual relations are elucidated in Sir Jolm Herschell's article, Liglit, " Encyc. 

 Mctrop.," vol. iv., sees. 1000, 1085 to 1097, 1113. Such investigations form at this 

 moment the frontier and vantage ground of future conquest, at once in Physics and 

 Chemistry. See also MaxwelFs papers on Elasticity, and on Faraday's Lines of Force, 

 " Camb. Phil. Soc. Trans." Dec. 10, 1855. 



It has been questioned to me, how far the fundamental fact is established, that iron, in 

 its several conditions of cast-iron, steel, and especially of malleable iron, is truly crystalline 

 at all ; whether it may not be possible that the texture of a long, silky-hbred bar of rolled 

 wrought-iron, is due simply to the extension and drawing out, long and fine, of the hetero- 

 geneous mixture of amorphous metal, and of included and uniformly distributed "cinder" 

 (i.e., oxides, silicates, and carburets), which might be supposed to form the mass, as first 

 ■withdrawn from the refinery or "balling furnace;" much like as a mass of bird-lime and 

 dry clay diffused through it, would probably roll or draw out. 



I cannot admit the force of the objection, or of the analogy. 



All the evidence we possess is in favour of iron having a truly crystalline structure. 

 Such is the structure of all so-called elemental solids, and assumed with distinctness 

 {cateris paribus) in proportion as they approach to chemical purity ; not only the analogy 

 here, but that nearer one with the whole class of all other metals, would be broken by 

 such assumption, the crystallizing power being evidenced in all, though developed with 

 very different facility, still in an unbroken chain, from bismuth and antimony, which crys- 

 tallize so readily, down to whichever may be held most difficult to obtain in crystallized 

 masses. But there is positive evidence of the power of cast-iron, of steel, and of malle- 

 able iron to assume the crystalline structure. The form of the integrant crystal is obvious ; 

 perfect crystals may be isolated ; they possess the property of distinct cleavage in well- 

 developed instances (Wohler) ; and the fresh surfaces, often of great size, possess the per- 

 fection of plane and of polish, that crystallization can alone confer. Other less broad and 

 obvious characteristics, such as difference of resistance to the action of menstrua in different 

 axes, might be urged. Or again, the diflerence of elasticity of (chemically the same) iron 

 in different states of development of the crystallization of the whole ; and diflerence of 

 elasticity in different directions in the same mass, following observable diflerenoes in the 

 prevailing directions of the crystalline axes. 



In a word, there appears no more good reason to doubt the truly crystalline arrange- 

 ment of the molecules of iron than there would be to doubt that an isolated octohedral 

 crystal of native gold, was truly a crystal, because, by the blow of a hammer, we can flatten 

 it into a spangle. The masking circumstance is alike in both cases. Metallic crystals are 

 all more or less malleable ; they are, therefore, susceptible of distortion (to almost any 

 extent, in the more malleable metals), and of re-formation, without external change, except 

 as to form, in the mass itself. 



