artillery officers, supplemented by data collected elsewhere, showed that the penetrations of the elongated rifled projectiles were variable, depending largely on the direction maintained by the axis of the projectile.
When the axis remained coincident with the trajectory or nearly so, the penetration exceeded that of the round shot of the same weight by about one-fourth, even at the shortest ranges, though greater charges were used for the guns firing the latter shot.
Whenever the axis of the projectile was turned, as the slightest obstruction would cause it to do, the penetration was greatly reduced.
There was a noticeable tendency to curve upward after entering an earth embankment.
The percussion shells, which were designed to explode on impact, attained usually about three-fourths of their entire penetration before bursting, and time-fuses, prepared to burn a certain number of seconds after leaving the gun, frequently became extinguished on entering the dirt.
With ordinary clay-loam, parapets and magazines required at least a thickness of sixteen feet to resist the 6.4-inch projectile (100-pounder) and twelve feet to resist smaller calibers.
In new earth not well settled, those thicknesses had to be increased.
Earthen parapets of the proper dimensions could not be injured greatly by rifled shells of any caliber less than 6.4 inches, and not permanently by those if the garrison were active in repairing the damage.
The moral effect of the shells as they went shrieking over the heads of the troops was frequently great.
In describing an engagement, a Confederate private soldier said that the reports of cannon were incessant and deafening; that at times it seemed as if a hundred guns would explode simultaneously, and then run off at intervals into splendid file-firing.
No language could describe its awful grandeur.
Ten thousand muskets fired in volleys mingled in a great roar of a mighty cataract, and it seemed almost as if the earth were being destroyed by violence.
The shells howled like demons as they sailed over the heads of the troops lying close to their improvised