Southeast Archeological Center
Cultural Resources National Park Service
PRIMARY DOCUMENTS (Page 4)
from] Report of Lieutenant T. B. Brooks
In accordance with your instructions, I have carefully examined, since the bombardment on the 10th and 11th ult., the condition of the batteries erected on Tybee Island, Ga., for the reduction of Fort Pulaski, and have the honor to respectfully submit the following report on the same, with remarks and deductions of my own, which you kindly gave me permission to add.
I. MORTAR PLATFORMS
For plans and dimensions see Plate IV [Figure 4, this volume].
The 13-inch mortar (1861 pattern) platforms used, may be described in general, as consisting, (1) of a flooring of three inch pitch pine plank, laid on ground well rammed and leveled; (2) on this flooring was placed a timber structure varying in the different platforms, but similar to the rail platforms....The chief difference was in the larger timbers used in our platforms, and in the fact that the center sleeper or cross piece was always omitted, except in some instances, blocks between the rails were used; also as our platforms were decked small outside rails or stringers, to support the ends of the deck, plank had to be introduced. [This is very unclear.] (3) On this framework a decking of "uniform stuff" furnished by the ordnance department, or common three-inch plank, was placed perpendicular to the line of fire, and fastened down in most cases, by side-rails, with four bolts in each.
Pickets three inches square and three and a half feet long, were freely used to stay the platform.
Plates of iron four and a half feet long, four inches wide by one-half inch thick, inches, [another unclear comment] were fastened on each platform, on which the eccentric wheels of the mortar-beds rested. How well this plan answered will appear from the following facts...
3. Burnside Battery (One 13-inch Mortar)
This platform is apparently in as good condition as the day it was put down.
Sergeant J.E. Wilson, U.S. Engineers, commanded this battery during the bombardment. He took care to fire the mortar in different parts of the platform, thus distributing the pressure and wear. The mortar was run forward nearly to the front of the platform, and then fired a number of times without being run in battery, until the recoil had carried it nearly to the rear of the platform, &c.
4. Sherman Battery (Three 13-inch Mortars)
...It is proper here to observe that in the Sherman and Burnside batteries, the platforms rest on a blue clay or mud mixed with sand and shells, while in the others fine pure sand only is found [implying this was the case for Battery Halleck as well].
5. Halleck Battery (Two 13-inch Mortars)
Both the platforms at this battery are like the Burnside, apparently uninjured....
The following summary embraces the most important facts relating to the mortar platforms constructed on Tybee Island:
Mortar Platforms Described in "Ordnance Manual" and "Heavy Artillery"
Four methods were used at Tybee:
From the above I believe the following rules should be observed in revetting under similar circumstances:
The timber used for the frames, was four by eight inch scantling. The bents (frames) were usually eight feet wide, and five or three feet high, resting on mudsills of the same stuff, one under each post. The bents were placed three feet apart horizontally, and were framed at the corners....
The sheathing and flooring were made of one and a quarter inch plank; two thicknesses being used on the top and one elsewhere. On this shell, seven feet of earth was placed, its sides sloping one on one and a half.
Entrances, with one and two doorways, were used, all so placed that if a shell burst outside, its fragments, moving in straight lines, could not reach the interior. Adjoining the magazine, the entrance [anteroom or antechamber?] was made five feet wide, to be used as a filling room for cartridges, and was arranged with shelves for cartridge bags.
The frames above described were not found strong enough, giving indications that they would fail by the breakage of the beams supporting the roof, and by the splitting of the shoulders of the posts on which the cross-timbers rested. Both difficulties were, in part, remedied, by placing an upright post in the centre of each bent, reducing the bearing of the cross-pieces supporting the roof to four feet, and relieving the vertical pressure on the side posts.
With this addition, none of the magazines failed, but there was evidently not surplus strength enough....
What effect a heavy mortar shell falling on such a structure, might have, was not experienced at Tybee.
The same difficulty was experienced in the magazines as in all structures where fine dry sand is exposed to the wind. It blew off very rapidly, thus not only diminishing the cover on the magazine, but filling up the covered ways, &c., &c. No permanency can be obtained except by sodding, or spreading over the surface a heavy coating of manure, which will cause grass and grain to grow.
Splinter proofs, in which the men forming the reliefs off duty might repose in comparative safety from the effects of shot and shell fired from guns, were built of pine logs, mud, and sand. Posts, four and a half feet long, were set in the ground, three feet apart, and of such slope as to be perpendicular to the rafters. On the top of these posts a longitudinal cap or plate was spiked. The rear revetting, about one foot high, was sustained by strong pickets, driven in the ground two feet, and standing two feet apart....
The rafters were laid in juxtaposition, the most prominent inequalities being hewn off to make better joints. Mud was plastered over the cracks, which made them completely sand-tight. Over this roof of timber three feet or more of sand was piled.
The longitudinal stick on top at the front edge of the rafters, to prevent the sand from running down in front, might advantageously be replaced by fascines or sand-bags.
Cross-traverses, of a double thickness of this uniform pine stuff, were placed at equal distances along one of the splinter proofs, intended to intercept fragments of shell, should one from a mortar fall through the roof and explode in one of the compartments. These would also serve to divide the space equitably among the occupants or reliefs....
These structures should evidently be erected so high that the floors may be dry at all times, and should be placed out of the line of fire of the enemy's batteries; hence midway between our own batteries would be the safest place, if the batteries are near together, as at Goat's Point, Tybee Island. For cross-section of splinter-proof shelter, see Plate III (Figure 3 in this volume).
I am, with great respect, your most obedient servant,