involved in the Construction of Artillery. 431 



CHAPTER XXII Molecular Constitution of WnoCGnT-lRON, and the Law of 



Direction of its Crystals or Fibre. 



SECTIONS. PAGE. 



193 Its molecular structure presents itself on fracture in one of three forms, or com- 

 bination of these, 244 



J 94 Law of arrangement of its crystals; though apparently opposite, it is essentially the 



same as in cast-iron, 244 



195 Normal structure; parallel crystals; fibrous rivet iron, 245 



196 Iron wire; ductility and intermobility of particles at all temperatures, .... 245 



197 Examples of analogous formsof cry stallization,iS:c., subject to the same law; minerals, 245 



198 Effects of change of dimension in the bar in altering the arrangement of its crystals, 246 

 199, 200 Effect of unequal expansion and contraction of the crystals in different a.xes; of 



change of diameter in the bar; of its mass, form, and surface; and the pressure 



of rolling 247 



201 Relations of the development of crystal to the "make" of iron, 247 



202 Wood fibre, how to be understood as applying to iron or other inorganic bodies; 



as only designating; form of crystallization, 248 



CHAPTER XXIII. — Effects ON Whought-Ieon of Forging into Great M.4saEs. 



203, 204 Precise nature of the forces applied in rolling, as compared with those in forged or 



hammered iron, 248 



205 Proof that rolled and hammered bars of the same iron differ only in molecular 



arrangement, and are mutually convertible in this respect, 249 



206 Great difference of ultimate tenacity due to this only, 249 



207, 208 Development and size of crystal, upon what dependent; relation to the "make;" 



occasional great size, 249, 250 



209 Foreign charcoal-iron; Swedish not advantageous for ordnance ; its crystalline 



structure ; Schaf haeutl's analyses of Low Moor iron, 250 



210 American anthracite and other iron, comparison with English and foreign ; none 



poSSeso advantages over British, 251 



CHAPTER XXIV. — Relation of Elasticity to the Crtstalline Axis. 



211 Discussion of Fairbairn's, Navier's, and E. Clarke's experiments, on the strength of 



boiler plates in the line of fibre, and across it, 252 



212 E. Clarke's experiments on extension in both directions; the elasticity of rolled iron 



is a maximum in the direction of the principal axes of the crystals; ultimate 

 resistance to explosive strains of wrought-iron in that direction, to that 

 transverse to it, as 7j to 1, 252 



CHAPTER XXV Effects of Forging into large Masses, on the useful 



Qualities of Wrought- Iron. 



213 Effects on molecular arrangement of large increase of mass, in connexion with the 



existing modes of manufacture, 253 



214, 215 Limit of the rolling process and commencement of that by hammering; serious 



difficulties and evils of large forgiugs; final limit as to their magnitude, . 253, 254 

 216, 217 True estimate of the value of powerful blows; the steam-hammer; its effect when 



the blow is excessive on very large masses, 255 



218 Direction in which to seek future extensions of our power to produce great masses 



of malleable iron ; the limit of useful size has for most purposes been already 



overpassed, 256 



3l2 



