Mid-nineteenth century designers of fortifications, especially those defending harbors and waterways, had a problem: Advances in ordnance and shipbuilding allowed naval vessels to deploy the same guns used by land-based forts while the ships' new iron armor made these moving targets seemingly impervious to the artillery from the forts. In 1867, Army Captain James T. Ryan offered a relatively simple solution to the issue. In a newly added publication to Special Collections & Archives - Specifications of a Revolving Iron Fort - Ryan laid out his plan to defend against ironclads by essentially constructing an ironclad on land and using it as a fort.
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| Rendering of Ryan's revolving iron fort from Scientific American. |
Ryan provided every minute detail for constructing his proposed fort without any images to help the reader imagine it, but his introduction offered a clear description of what he had in mind. "The fort will be a modification of the iron turrets employed upon the Monitor vessels of the Navy," he wrote. "It will be larger, heavier in all its details, carry more guns and posses in some of its modifications the removal of defects discovered in Monitor turrets in battles they have encountered since the latest of them were designed."
The main part of Ryan's fort was this Monitor-type turret, but he included a 10-foot wide glacis surrounding the fort in his description, so from a distance the fort could resemble an entire Monitor vessel rising out of the ground. Like a Monitor, Ryan's fort would rotate, so it could fire in any direction, but unlike the ship, the fort would be equipped with eight 15-inch guns. Ryan also designed the fort with a compressed air system that easily moved the guns into and out of their firing positions.
To this point, Ryan's idea wasn't entirely new. An 1863 article in The New York Times described and illustrated a system for harbor defense designed by Theodore M. Trimby that included two towers "to be rendered impregnable to shot and shell by an iron covering on the outside." These towers would also rotate but would have two tiers of guns, with 30 guns per tier. Not surprisingly, the article credited the action between the Monitor and the Merrimac as the inspiration for designing this new system.
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| The grounds of the Naval Academy with a monitor used in training midshipmen in the Severn River. |
What made Ryan's idea unique was making his land-based Monitor turret essentially a floating fort. The entire turret structure would rest atop a tank filled with water with a center pintle running through the tank and providing stability. This design was intended to make rotating the turret easier and allowed it to move in another dimension. "The fort being thus afloat in a reservoir , can be elevated or depressed at will within certain limits, by means of an overflow valve attached to the reservoir," Ryan wrote. A rotating iron fort itself could be somewhat of a moving target.
However, the whole thing remains theoretical as Ryan's fort was never built. It did garner a lead article in an 1868 issue of Scientific American, which featured an illustrated cross section of the proposed fort, but the Army's Board of Engineers for Fortifications had already rejected the idea of building it. The board concluded in 1867 that the fort would be too costly compared to other turret designs and traditional forts; would still require traditional fortifications to defend against land-based attack; could not be rotated and stopped with enough precision to allow for accurate, efficient fire; and would be too small to accommodate the eight guns along with the men and supplies needed to fire them. When directed to reconsider the plans in 1869 by a joint resolution of Congress, General William T. Sherman sent the 1867 report and a new report from the same board containing skepticism of whether the fort would truly be impervious to shot, to which the general added that he found the fort "useless and impracticable."
Turrets would soon be incorporated into fortification design, but they would not be of the Monitor type advanced by Ryan. Instead, Ryan's plans remain an interesting idea among many housed in Nimitz Library's Special Collections & Archives.
Works Cited
Ryan, James T. Specifications of a Revolving Iron Fort, Mounting Eight XV-Inch Guns. New York: B. H. Tyrrel, 1867.
"Hydrostatics Applied to Revolving Iron Forts." Scientific American 19, no. 26 (December 23, 1868): 401-402. https://doi.org/10.1038/scientificamerican12231868-401.
H.R. Ex. Doc. No. 41-17 (1869).
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