2fiG JNIr. Mallet on the Physical Conditions 



arrangement ; the principal axes assuming the directions of least pressure. 

 As the planes of weakness in •wrought-iron are the planes of cleavage of its 

 original crystals (i. e. the crystals in its mass as manufactured), so when these 

 are originally confused and partly transverse, the bending double a bar of such 

 a character (i. e. of bad iron) becomes doubly difBcult : — 1st. Because of the 

 original crystals transverse to its length ; 2nd. Because of those induced in the 

 process ; the rate of bending, therefore, must be proportionably very slow. 



235. The author is not aware that any explanation on just physical groimds 

 lias been before oifered of these well-known phenomena. Swedenborg, in his 

 large work, "Regnum Subterraneum sive Minerale, de Ferro," published in 

 folio at Leipzig in 1734, Par. xxv. pp. 215, 267, 270, has described with much 

 accuracy several of the forms of crystalline arrangement of wrought-iron, and 

 of its passage into steel ; and some interesting observations on the crystalline 

 fracture of wrought-iron, by M. Aug. Malberg, will be found in the " Bui. du 

 Musee de I'lnd. de Brux.," 1846 ; but neither these, nor any other author, appear 

 ever to have grasped the leading thought, which is the key to the question. 

 Upon these principles depends — 



28. — The relative Injury done by the Stroke of Shot, to Guns of different 



Materials. 



236. Experiments were made in France, at Lafere, in 1836—37, by firing 

 round shot en ricochet at 100 metres range, at equal-sized guns of cast-iron and 

 of gun-metal, which proved decisively in favour of the former as respected the 

 resistance offered to injury thus caused; every diametric stroke of round shot, 

 even with very reduced charges, producing dinges, or indentations, upon the 

 bronze guns, reaching to the interior, to such an extent as to prevent the possi- 

 bility of afterwards ramming home a shot. (Thierry, " Applic. du Fer, 6L-c." 

 2nd partie, p. 125.) 



237. It is believed, that no similar experiments have been made on any 

 wrought-iron gun ; but the point is one not difBcult to predict accurately upon. 



The stiffest (or most rigid and tough) and heavest material, is that which 

 must suffer least by a given impulse from a liarder body, provided that fracture 

 do not result from the blow. 



