The three breaching batteries - Sigel, Scott, and McClellan - were established at a mean distance of 1,700 yards from the scarp walls of Fort Pulaski.
The circumstance, altogether new in the annals of sieges, that a practicable breach, which compelled the surrender of the work, was made at that distance in a wall 7 1/2 feet thick, standing obliquely to the line of fire and backed by heavy casemate piers and arches, cannot be ignored by a simple reference to the time-honored military maxims that "Forts cannot sustain a vigorous land attack," and that "All masonry should be covered from land batteries."
A comparative glance at the status of military science as regards breaching prior to the invention of rifled cannon will enable us to form a tolerably correct estimate of the importance to be attached to the results developed by this improved arm of the service. A standard military work furnishes the following extract:
An exposed wall may be breached with certainty at distances from 500 to 700 yards, even when elevated 100 feet above the breaching battery; and it is believed that in case of extreme necessity it would be justifiable to attempt to batter down an exposed wall from any distance not exceeding 1,000 yards; but then the quantity of artillery must be considerable, and it will require from four to seven days' firing, according to the number of guns in battery and the period of daylight, to render a breach practicable.
During the Peninsular war breaching at 500 to 700 yards was of frequent occurrence, and at the second siege of Badaajos fourteen brass 24-pounders breached an exposed castle wall backed by earth alone, and consequently much weaker than a scarp sustained in the rear by heavy piers and arches, in eight hours, at a distance of 800 yards.
Experiments of breaching with rifled guns have recently been made. I shall notice two cases:
In August, 1860, experiments with Armstrong's rifled guns were made against a condemned martello tower at Eastbourne, on the coast of Sussex, England. The tower was of brick, fifty-six years old, and designed for one gun, the wall being 7 1/2 feet thick at the level of the ground and 5 3/4 thick at the spring of the vault, which was 19 feet above the ground. It was 31 1/2 feet high, 46 feet exterior diameter at the bottom, and 40 feet at the top. The pieces used against it were: one 40-pounder of 4 3/4-inch caliber, one 82-pounder of 6-inch caliber, and one 7-inch howitzer throwing 100-pound shells. A practicable breach, 24 feet wide, including most of the arch, was made with an expenditure of 10,850 pounds of metal, at a distance of 1,032 yards. The projectiles expended were: 40-pounder gun, 20 solid shot, 1 plugged shell, 43 live shells; 82-pounder gun, 19 solid shot, 8 plugged shells, 36 live shells; 7-inch howitzer, 2 plugged shells, 29 live shells.
Projectiles that failed to hit the wall are excluded from the above table.*
General Sir John Burgoyne, in his report upon these experiments, says:
Trials were subsequently made to breach a similar tower from smooth-bored 68 and 32-pounders at the same range of 1,030 yards, and the result may be deemed altogether a failure, both accuracy of fire and velocity of missiles being quite deficient for such a range. At 500, or perhaps 600, yards the superiority of the rifled ordnance would probably have been very little, if any.
Experimental siege operations for the instruction of the Prussian army, comprising the demolition of the defective and obsolete fortifications at
* Reference is to table on the map showing position of the batteries, & c., to appear in Atlas. The table shows that 4,079 shell and 914 shot were fired.
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