involved in the Construction of Artillery. 301 



cally and advantageously applied, — the same section of iron doing 

 much more resisting work, as applied in the gun built up in com- 

 pressed and extended plies, than in any solid or other gun. 

 7°. The introduction thus into cannon, of a principle of elasticity, or 

 rather of elastic range (as in a carriage-spring divided into a 

 number of superimposed leaves), greater than that due to the 

 modulus of elasticity of the material itself, and so acting, by dis- 

 tribution of the maximum effort of the explosion, upon the rings 

 successively recipient of the strain, during the time of the ball's 

 traject through the chase, as materially to relieve its effects upon 

 the gun. 



In a word, we secure better material, and apply it better in place. It is 

 upon these principles that the author has designed for Government the great 

 36-inch mortars, to throw a shell of a yard in diameter, and weighing in flight 

 above 3000 pounds, which are now in process of manufacture. 



305. In conclusion, it will be desirable to offer some remarks, in refutation 

 of the principal objections that have been made, or most obviously present 

 themselves, to wrought-iron guns generally, and to built-up guns, or those 

 formed in several separate pieces, in particular. 



These are pretty fully enumerated in the extracts from Reports made to the 

 American Government on wrought-iron guns (Note Z) ; and refer either to — 



1°. Difficulties and uncertainties of manufacture, weldings, &c., common 

 to all large forgings. These we fully admit, and, in what precedes, 

 propose altogether to evade, by another and a better method of 

 construction, which dispenses with large forgings. The special 

 modes of failure and their causes, which many of the largest and 

 most recent cases of proof of heavy wrought-iron guns forged in 

 one piece have presented, are recited in Note AA. 



2°. That all that can be gained by the use of wrought-iron for guns is 

 comprised in lightness and strength ; that the former is, in fact, 

 not desirable, because, unless the weight is, in field guns, to that 

 of the shot, at least as 140 : 1, and in battering guns as 200 : 1; — 

 the recoil is too great, and is inconvenient. This objection rests 

 VOL. XXIII. 2 u 



