involved hi the Construction of Artillery. 



277 



much to be desired in relation to the construction of artillery ; for, whatever 

 be the law or amount, of decrease of strength, as against the bursting strain, due 

 to the coincident longitudinal extension and normal compression, there seems 

 enough already known to warrant the supposition that the reduction is often 

 serious, and that it may be much and unnecessarily increased, by an injudicious 

 position given to the trunnions, and by their rigid fixation, into massive and 

 unyielding metallic gun-carriages. And, as the longitudinal strains are a 

 minimum, when the gun is not sustained on trunnions, but is supported along 

 its whole length, and the recoil firmly resisted, by a fulcrum behind the breech 

 (like the barrel of a musket in its stock), so there can be little doubt that a 

 gun mounted in this form will resist the largest charge in proportion to its 

 scantling and material, or, with any ordinary charges, will last the longest. 

 Thus the cumbrous cannon of ancient times, whether accidentally or not, 

 possessed in this respect another element of strength. (Note A, " Ancient Ser- 

 pentines.") 



32. — General Comparison of the Constructive Constants of the Materials for 



Ordnance. 



264. Having thus considered in succession, the relational characteristics of 

 each of the four chief materials for the fabrication of artillery, and some of the 

 most important specialties that belong to each, we arrive at a point where, in 

 the four following Tables, are presented in one view the principal deductions 

 which the discussion warrants : — 



Table XIV. 

 Of the Physical Properties of the principal Materials of Construction for Artillery, from British Data. 



Note.— The moduli of Elasticity are Tredgold's. The values of i, from the means of various experimenters, as also the vahies of 



coluniiis S, 4, 5, and 6. 

 VOL. XXIII. 2 o 



