inaolved in the Construction of Artillery. 299 



produce rupture, we find that although the strain is so much less on the 

 annealed wire, the work done to produce elongation and rupture is far greater 

 in it, than in the hard wire: — 



Hard, . . ^ (52 X 0-004) = 0-104, 

 Annealed, . H^O x 0-200) = 3-000, 



or in the proportion of nearly 29: 1, — a result, which, if even approximately 

 correct, gives abundant corroboration of the views herein enunciated as to the 

 value of soft and ductile wrought-iron for artillery. A paper of Baudrimont's, 

 on the diminution of tenacity due to annealing (Ann. de Chim. etPhys., t. 60, 

 p. 78), is deserving of attention here. 



35. — Of Trunnions or other Fulcra^ in Belation to Built-up Guns. 



301. In the attempts heretofore made (in modern times), to construct built- 

 up -wrought-iron guns in single-ply rings, trunnions have been formed, attached 

 to one of the rings, and the gun has been mounted as much as possible in the 

 ordinary way. It has been already shown (chap. 31) that every gun, whether 

 solid or built up, is weakened by this mode of mounting, but when applied to 

 built-up guns in rings, its effects are fatal ; the recoil at every discharge tends 

 to dislocate the rings from each other, and to move them relatively forward 

 upon the internal longitudinal bars ; a circumstance that has actually produced 

 the destruction of some such guns tried at Woolwich. 



302. Wrought-iron built-up guns of large size should, therefore, for every 

 reason, be so mounted, that the whole force of the recoil should be expended 

 upon a fulcrum placed directly in the line of the axis, and behind the breech, 

 much in the same way as the ancient wrought-iron cannon (bombards, serpen- 

 tines, and chamber pieces) were mounted (Note A), and that this can be done 

 with perfect facility, and without sacrifice of any of the requirements or advan- 

 tages of the usual method of mid-length trunnions, probably no competent artil- 

 lerist or mechanical engineer will be found to doubt ; although, because a devia- 

 tion from the " routine" of some centuries, any such arrangement is certain to 

 meet with opposition in the first instance, — in fact, so far from the abandonment 

 of trunnions being a disadvantage, it would be attended with the immense ad- 



