involved in the Construction of Artillery. 413 



tried, one failed at the 150th fire, by tlic trunnion band becoming loose, and another, at 

 the 450th fire, by the opening of the welds, the results, so far, are not sufficient to warrant 

 a definite conclusion as to the merits of this mode of fabrication. So far as it has been 

 tested by this Department, wrought-iron has not proved a good material for the manufac- 

 ture of field-guns ; and as the difficulty of fabrication increases with a greater quantity of 

 metal, it is less suitable for those of a larger caliber. The greatest objection, and appa- 

 rently an insurmountable one, is the difficulty of welding the parts together perfectly, and 

 the still greater difficulty or impossibility of ascertaining whether the welds are perfect or 

 not. Besides, the effect of heating is to render the iron more porous, and of less specific 

 gravity and tenacity ; and, when often repeated, is known to destroy the good qualities of 

 the best refined iron. When tlie bars are of small size, as in gun-barrels, the hammering 

 compresses and re-unites the particles, and corrects these defects ; but in large masses the 

 effects of the hammer do not reach the interior of the mass, which is, consequently, left 

 open and spongy, although the metal on the surface, and to a slight depth, is compact and 

 fibrous. 



" The objects attempted to be gained by the use of wrought-iron for cannon are — 

 1st, lightness; and 2nd, strength. 



" 1st. — Reasoning from the successful use of that material for small arms, it has been 

 supposed that a skilful and careful fabrication would effect these results. But lightness, 

 below a certain ratio, is not desirable ; it is positively injurious, for light guns can be used 

 only with light charges. Field-guns cannot be conveniently served when they have less 

 than loOlbs. of metal to each pound of shot ; and battering-guns require at least 2001bs. 

 of metal to each pound of the shot. With any less weight, the service of the gun is very 

 difficult, from its excessive recoil ; therefore, lightness is not a desirable point in the con- 

 struction of cannon[?]. 



" 2nd. — Strength. As this is always desirable, it should be eflf'ected if possible, but not 

 at the expense of any other important point. If it were possible to fabricate sound and 

 strong guns of wrought-iron, they would be found deficient in hardness. The projectiles 

 used are of cast-iron, a material much harder than wrought-iron ; consequently, the 

 wrought-iron gun is soon indented and worn so much as to prevent all accuracy in firing, 

 and it then is worth little or nothing[?]. 



" Leaden balls are used in small arms, but they are inadmissible in cannon, as the great 

 heat of the exploded gunpowder melts the lead more or less, and changes the form of the 

 ball, thereby reducing its range. Besides, lead has not sufficient tenacity to enter hard 

 substances, and therefore is not a suitable material to be used against ships and batteries. 

 Wrought-iron is also more liable to injury from rust, than bronze or cast-iron ; and the 

 smallest crack, admitting moisture, would, of itself, in time, seriously injure the gun. The 

 VOL. XXIII. 3 H 



