Iron Embrasures for the Batteries on Morris Island

Another problem faced by the engineers and artillerists preparing the breaching batteries on Morris Island was the embrasures through which the guns pointed over the parapets. As the embrasure is an opening in the fortification, these are always weak points in the works. But without them, the gun crew must work the gun over the parapet and might be exposed to enemy fire. In defensive works, with more time devoted to perfection of the opening, engineers used wood planking to define the embrasure. Normally, for earthworks such as seen around Vicksburg, Petersburg, or other siege lines of the Civil War era, the engineers used gabions filled with dirt.

But the nature of Morris Island presented a problem with that practice, as Major Thomas Brooks explained in Note No. 12 of his report:

Gabions, fascines, and hurdle work, when used for revetting the cheeks of embrasures, were found to leak the fine dry sand used in the construction of our works, unless filled or backed with sandbags. This remedy adds to the expense and labor, and is, besides, not very durable. Sods suitable for revetting are very scarce on this coast.

Sand-bags alone lasted a long time in Battery Hays, but its guns were fired at an elevation of 5° and upward. These high elevations gave a far less injurious cone of blast than low ones. The raw hides used for lining sand-bag embrasures were soon blown out (particularly by the Wiard gun), in spite of our efforts to make them fast by means of notched pickets.

Looking for a more durable solution Brooks made the most of the materials on hand. Remember this wreck between Folly and Morris Island?

The Ruby looks picked over. And more than just damage done while recovering the blockade runner’s goods. She was practically scrapped in place as the Federal engineers turned salvaged materials into something to resolve the embrasure problem:

To overcome these difficulties, a boiler or sheet-iron casing or lining was made from iron plates obtained from the wreck of an iron ship (a blockade-runner) which came ashore at Light-House Inlet. The splay, the dimensions of the throat, size of cheeks, length and inclination of sole, and thickness of plates used, were varied to suit the case. For direct firing, the splay may be 25°, or even less.

To set the casing, the genouillère is first finished, and the sole of the embrasure given its proper slope. On this sole is placed the iron casing, its directrix having the proper direction. Sand-bag merlons were built on each side, to which the lining was anchored by means of wires and crooked iron rods which were made fast to its cheeks and rings.

Brooks provided an illustration of these improvised embrasures.


Brooks recorded the iron as a quarter-inch thick, weighing 10.4 pounds per square foot. Eight of these went in to the second parallel. The illustration helps explain a mantlet configuration used for one of the gun positions in Battery Rosecrans:

This mantlet is of bullet-proof iron plate, arranged as a hanging door, which closes the throat of the embrasure. In this door is a cut or slot for the double purpose of allowing the rammer and sponge staves to pass through when loading, and for sighting the piece. A small scantling of hard wood, with a rope attached to its upper end, is made fast to one side of the door, and acts as a lever to raise the door when the gun is fired. The swing bar of 1-inch round iron, upon which the hinges of the door are hung, has a collar at each end, to enable the cheeks of the carriage to resist lateral pressure. The sole was given a counter slope of 5°. The wings prevent the casing from being carried out by the force of the blast.

The one gun position supplied with a mantlet was active against Fort Sumter during the bombardments through September. Because of the elevations required to reach that target, the gun crew might otherwise be exposed to Confederate sharpshooters. The mantlet arrangement allowed the crew to work with some measure of safety.

In conclusion, Brooks suggested, “The satisfactory results obtained from the use of these casings indicates that sheet and boiler iron should form part of the siege material furnished for military operations in a sandy country.” He added that the plate was later easily converted to Sibley stoves during the winter months.

An inglorious end for once sleek blockade runner.

(Citations and illustration from OR, Series I, Volume 28, Part I, Serial 46, pages 321-2.)