Effect on Wood

—The effect of a projectile fired against wood varies with the nature of the wood and the direction of the penetration. If the projectile strikes perpendicular to the fibres, and the fibres be tough and elastic, as in the case of oak, a portion of them are crushed, and others are bent under the pre ure of the projectile, but regain their form as soon as it has pa ed by them. In consequence of the softne of white pine, nearly all the fibres struck are broken, and the orifice is nearly the size of the projectile; for the same reason the effects of the projectile do not extend much beyond the orifice; pine is therefore to be preferred to oak for structures that are not intended to resist cannon projectiles, as block-houses, etc.