434 Mr. Mailet on the Physical Conditions 



SECTIONS. PAGE. 



271 The construction, by rolling, of wrought-iron guns, cheaply and readily, up to about 



12-poundei-s, offers no difficulties, 282 



272 With enlarged calibers the rolling process must still be adopted; why and how, 



considered, 283 



273 Analysis of the forces acting upon a gun when fired, 283 



274 The limit at which no addition to thickness adds to resisting power; Morin's, Dr. 



Robinson's, Dr. Hart's, Barlow's formula for resistance of cylinders, . . 284, 285 



275 Barlow's parado.\ical result, not the correct conclusion from his reasoning, . . . 285 



276 The limit of thickness for any material soonest reached with cast- steel, .... 285 



277 The gun bursting at one or both ends of a diameter, does not affect this limit, . 286 



278 Effect, the caliber continuing the same, of merely removing the material further 



from the axis, 286 



279 Effect, the caliber continuing the same, of separating the whole thickness into con- 



centric lamina;, initially compressed and extended, 287 



280 Theoretic increase of strength thus effected for same caliber and thickness, . . . 287 



281 The conditions of 278, 279, combined; results, 288 



282 Built-up guns of wrought-iron on the preceding principles 289 



283 Calculation of strength in practice, 289 



284 Investigation of comparative and absolute stress and resistance of the external rings 



and of the longitudinal bars, 290 



285 Eatio of distress in guns made solid, and of the established models, tangential 



and longitudinal, 291 



286 Precautions as to radial junctions, 291 



287 Their enlargement at instant of explosion, evanescent; example in a 10-inch gun, 291 



288 Reinforce rings, shrunk-on, not new, but the construction here proposed is so, . 292 



289 In practice, precise temperature of the successive rings unimportant 292 



290 Discussion of the physical conditions of wrought-iron, contracting from high tem- 



peratures under strain, . 293 



291 , 292 The work done divided between elongation of the bar and residual strain, . . . 293 



293, 294 Practical deductions as to shrunk-on rings, for whatever purpose, 294 



295 The cooling may be slow or sudden, as with wheel tyres ; distinction between those 



and gun rings; for the latter the cooling to be slow, and the iron annealed, . 295 



CHAPTER XXXIV Of the Relations BET^VEEN Annealing and Tenacity. 



296 Experimental knowledge deficient; condensation and arrangement of crystal by 



rolling, &c., increase tenacity ; annealing appears to diminish it ; the work 

 done at rupture may, however, be a constant, 296 



297 The annealing temperatures of metals not determined; apparent relations to fusing 



temperature; annealing in the more fusible metals; Baudrimont's researches, 296 



298 Changes of density by rolling, and by annealing iron, copper, gun-metal, . . . 297 

 299, 300 Researches of the Franklin Institute, of M. Pay en; the work done at rupture in 



both states deduced from his results; confirm the views of the text as to value 



of wrought-iron for artillery, 298 



CHAPTER XXXV. — Of Trunnions or other Fulcra in Relation to Built-up 



Guns. 



30 1 Trunnions, as hitherto attached to single- ply ring guns ; destruction through effects 



of recoil, 299 



302 In built-up guns the recoil should be borne by a fulcrum in line of axis against 



the breech. Advantages of abandoning trunnions in all cases ; absorption of 

 recoil not by dead weight, but by elastic material, 299 



