John Stevens’ talented son, Robert, inherited his father’s passion for nautical invention and in 1812 he submitted to the Navy Department a promising design for a fleet of “harbor protection” vessels whose basic concept, he averred, derived from the common hard-shell turtle. Stevens’ mobile batteries were very low in cross-section, powered by screw propellers, which gave them considerable maneuverability, and the main part visible above water consisted of a steeply raked, stoutly armored cupola (the turtle’s shell) whose parabolic arc would have greatly vitiated the kinetic energy of heavy solid shot, allowing the shallow-draft “turtles” to hover around an invading fleet, hurling heavy-caliber shells into it from many angles. These ships were not intended to replace permanent harbor fortifications, but to augment them. Sea-worthy, they were not, but then as they would be employed only in shallow coastal waters, they didn’t need to be; fast, they were not, but again they were maneuverable enough to present a tough, low target, while maintaining a brisk and galling fire from their own low-lying batteries. Some naval authorities were impressed with Stevens’ design and saw considerable utility at a relatively moderate cost. But in the end, Stevens was told his proposals needed “further study” (a phrase which was, even then, the bureaucratic kiss-of-death) and was sent on his way with thanks, but no stipend and no contract.
Another inventor, Thomas Gregg, working independently of Stevens but in the same year (1812), was awarded a patent for an ironclad-ram design that featured slab-sided plate angled to 18 degrees – in other words, basically the very model of what would later be known as the CSS Merrimac.
By the mid-1820s, improvements in metallurgy and cumulative experiments in ballistics had greatly increased both the reliability and the effectiveness of the shell gun. Its persistent inventor, Col. H. J. Paixhans, would finally reap the fortune his lethal invention entitled him to, for the French Navy adopted these improved weapons and began systematically installing shell-gun batteries on its warships. Other nations were either developing their own shell-gun designs or considering large-scale purchases of the Paixhan guns, so whatever advantage the French had gained would only be temporary. The question now shifted to matters of defense, ways to extend France’s lead by devising effective ways of protecting its vessels against enemy shellfire. Paixhans had dutifully been studying that aspect of the new, slow-motion, European arms race and his recommendation to the Comite Consultatif de la Marine was remarkably similar to that reached by the indefatigable Stevens men in America, based on their own independent studies and experiments: iron plates, backed by criss-crossed layers of seasoned-oak planking, offered the most reasonable, affordable, form of protection against both heavy-caliber solid shot and shells alike. The French bureaucrats duly considered this proposal from every angle, but their conclusion was inevitable, given the existing constraints of budgets and technology: Yes, it WAS perfectly feasible to sheath a man-of-war in the suggested manner, but the increase in weight would force a significant reduction in the number of guns that could be carried, and the costs involved would prohibit all but a handful of ships to be so modified., both now and in the foreseeable future. Discouraged, though not especially surprised, Paixhans went back to selling his shell guns on the open market, gradually amassing a considerable personal fortune.
So the evolution of ironclad warships reached a brief period of stasis, but one which the momentum of progress would not allow for long. The late 1820s also saw exponential developments of new, larger, more powerful steam engines, and their ever-widening adoption as the main source of propulsion for naval vessels. No one disputed the advantages of steam power in terms of speed, range, and maneuverability, but by mounting a steam propulsion plant inside a warship’s hull, you also gave the enemy a precise and very vulnerable target to aim for. Where the Nelsonian ships-of-the-line had achieved victory by massed random broadsides that would more or less pummel the whole target down its length, smothering it with such a volume of metal that a certain percentage of hits were bound to dismount guns, shatter masts, and pulverize rigging, to say nothing of enemy sailors, the new steam-driven warships could be critically disabled by a few well-aimed hits in the known location of the power-plant. Worse: a lucky hit to the enemy’s boilers could generate both explosions and fires that could gut or sink the targeted vessel in only a fraction of the time required to hammer it into submission with conventional broadsides. THAT portion of a vessel simply HAD to be girded with extra protection, or its vulnerability would cancel-out the very advantages conferred by steam power in the first place. Experts in all the leading naval powers were pondering this paradox, and typically were reaching the same sort of conclusions as those outlined by the respected officer Charles Napier in a memo he submitted to the British Admiralty in 1827:
It has been proven that a combination of oak timbers, iron plate, and bales of cotton or reams of paper, four feet thick, will be sufficient to protect the boilers and engines against an eighteen-pound shot, and without such protection, a steam boat is entirely useless in war.
An upsurge in tension during the late 1830s, occasioned by some provocative movements by large, powerful English squadrons, created a bit of a war-scare, which caused the wheels of progress to be lubricated again by the flop-sweats of anxiety. The Stevens brothers, Robert and Edwin, had never ceased experimenting and testing, despite their repeated rejections from the Navy Department. Now, rather suddenly, they found themselves being courted. Encouraged by the fact that in 1841, President Tyler had convened a blue-ribbon panel to study any new ideas the brothers might wish to present, they gathered their drawings and data tables and traveled once more to Washington, where they found a more cordial welcome than previously.
The Stevens boys had by then become self-taught experts in metallurgy and ordnance; at their own expense they had developed a new type of four-inch iron armor plate and extensively tested it against the fire of the most powerful naval gun then mounted, the formidable 64-pounder. Impressed by their data and conviction, the Navy arranged a set of official tests at the ordnance-proofing range at Sandy Hook, New Jersey, and those tests confirmed that the Stevens’ new armor plate was indeed as stout as they claimed. On January 13, 1841, Robert and Edwin were awarded a government contract for $600,000 to perfect their design and devise ways of applying it to new and existing warships; it was a vindication that must have been as sweet as it was overdue!
By that time, the prospects of a new naval war with Great Britain seemed
more than likely, and there was great concern about the vulnerability
of Americans three most vital nautical gateways: Boston Harbor, New
York Harbor, and the Chesapeake Bay. Each water course was deep enough
to accommodate the heaviest British warships, and each was so wide-mouthed
that no conceivable system of land-based forts, no matter how large
and well-armed, could possibly cover those entrances; the best that
could be hoped for was that the networks of forts might inflict some
damage, and serve as speed-bumps to delay an invasion, buying time for
the militias of the threatened regions to be mobilized – the example
of the War of 1812 did not inspire confidence in that strategy, but
at the moment, it was the only one available. What would most likely
happen was that the British armadas would massively suppress the coastal
forts by smothering them with sheer weight of metal, while the actual
invasion fleet scooted through the middle and passed too far inland
for the weaker secondary forts to do more than harass the attacking
flotillas as they sailed majestically by.
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