430 Mr. Mallet on the Physical Conditions 



SECTIONS. PAGE. 



155 Authors who have treated on the subject 221 



156 General formula for modern gun-metal ; composition of old, 221 



157 Table IX. — Physical properties of the atomic alloys of copper and zinc, and of cop- 



per and tin, 221, 222 



158 Physical conditions in bronze demanded for gun-metal, 223 



159 Relation of composition to specific gravity, 223 



160 Extreme find mean alloys adopted in the chief gun-foundries, 223 



161, 1G2 Segregation of the alloy; heterogeneous constitution of a bronze gun cast verti- 

 cally 223, 224 



163 Constitution of the segregated alloy, 224 



164 Peculiar phenomena attending the segregation; erroneous explanation, .... 225 



165 Probably true theory of the phenomena proposed, 225-227 



166 Change in the constitution of the alloy produced in melting, 227 



167 General formula' for the normal and segregated alloys, 228 



168 Atomic discussion of the four principal alloys in use; the best known alloy is 



strictly atomic, 228 



169, 1 70 Discussion into rational formula; of the normal and segregated alloys, as indicating 



the physical constitution of gun-metal, 229-231 



171 Berthier's analysis; formula of bad gun-metal, 231 



172 Analogies with Muntz metal ; injurious effects of ternary alloys, 232 



173 The tin and copper probably never separate but as alloys, 232 



174 Effect of difference of specific gravity in segregation in vertical columns, . . . 233 



175 Difference in the part played by the " dead heat" in cast-iron and in bronze gun- 



casting; value of increased heat in the latter, 233 



176 The best temperature for pouring the fluid metal, 233 



177 The more rapidly the casting can be cooled, the better; Darcet and Dussausoy's 



experiments; effects of sudden cooling on the gun-metal, 234 



178 Method of chill-casting bronze guns, proposed, 234-236 



179, 180 Ternary alloys injurious, but valuable results obtainable from alloying gun-metal 



with sodium in minute quantity, sustained by Berthier's analysis, and probably 



by Spanish artillery, 236-238 



181 Difficulties and uncertainty of bronze gun-casting; wrought-iron would be an ad- 



vantageous substitute, 238 



182 Baron Hackewitz's electrotype bronze guns, 238 



183, 184 Bronze and wrought-iron cannot be united in the same piece of artillery, . . . 239 



CHAPTER XX Molecular Constitution of Bronze or Gdn Metal in 



Cannon. 



185 Character and colour of its fracture in normal metal; it is crystalline, .... 240 



186 Proof that the principal axes of the crystals in mass are arranged in accordance 



with the general law, 240 



187 Abnormal arrangements in bad gun-metal, 241 



188 Effects of bursting fractures on internal crystalline arrangement 241 



CHAPTER XXL— Steel as a Material for Cannon, in Relation to its Work- 

 ing Properties. 



189 Cast-steel that alone fitted for ordnance; Styrian steel, 242 



190 Krupp's cast-steel, 242 



191 Difficulties of working steel ; high cost of workmanship; other objections, . . . 243 



192 Objections as to its form of fracture, and small limiting thickness in guns, . . . 243 



