involved in the Construction of Artillery. 345 



greater llian those of small bulks. Less tlian one-half of this charge would probably be 

 sufficient in practice for every requirement. 



As the relation between aerial resistance and momentum, however, has been shown 

 to be as nearly 2 to 1 in favour of the 36-inch shell, there can be no doubt that, with ;i 

 proportional charge, a range very much above that of a 13-inch shell could be obtained, 

 and tliat an extreme horizontal range of from three to four miles might be anticipated. 

 Such extreme ranges, however, are not the important question or advantage as respects these 

 large shells, whose most valuable and effective uses, would probably be found at much less 

 distances, or within a range of 1000 yards. 



Before dismissing the subject of the penetrative power of these large shells, one more 

 remark should be made. 



In the destruction of buildings, &c., it is all important that the shell before explosion 

 should enter the interior. This always involves questions of relative inertia, in which the 

 greatness of the mass of the falling shell, as opposed to the mass of the body to be moved or 

 pierced, whether arch, floor, or solid earth, are elements. It is almost inconceivable how 

 vastly greater will be the shaking and dislocating effects upon structures, of a mass falling on 

 them of 1| tons weight, as compared with the insignificant weight (200 lbs.) of a 13-inch 

 shell, which with difficulty pierces through a well-made brick arch, of moderate span, 

 and three bricks thick. It seems probable, that not one of the cascmated forts of the 

 Russian fortresses could sustain the shock of the fall of a 3G-ineh shell, without total dislo- 

 cation. 



Authors on military architecture state that vaults of masonry of 40 inches in thickness 

 are to be considered bomb-proof, and the tables of fire give a penetration into masonry of 

 13-inch shells, at extreme ranges, of only 3 or 4 inches. At the siege of Tournay, in 174.5, 

 forty or more bombs are said to have fallen upon the magazines, without doing much in- 

 jury. One element, however, seems to be omitted by all authors who have treated of this 

 subject, namely, the span of the arch, the weakness of which, to resist the shock of shells, 

 must increase more rapidly than the width, for equal depth of voussoir, and very much must 

 depend upon the character as to weight, elasticity, and crushing resistance, of the material 

 itself of the arch. A heavy, moderately soft, tough brick arch, well jointed and bonded, 

 will probably offer a much greater resistance, for given dimensions, than one of hard, elastic 

 stone, unless the latter be in very heavy blocks. 



The explosive power of any shell being, as stated, directly proportionate to the weight 

 of powder it contains, it might seem at first that the destructive effect of the explosion in 

 shaking and levelling buildings, &o.,will have a focus or area of action in the like proportion. 

 The explosion of a shell may be regarded, at the first moment, as equivalent to the sudden 

 creation of a sphere of elastic gases, equal to, say, about one thousand times the volume of the 

 contained powder. This produces, by its sudden expansion, a blow or pulse upon the sur- 



