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the swell of the shells, at the head of the animal. The inside was capable of containing the operator, and air, sufficient to support him thirty minutes …

      —David Bushnell, “General Principles and Construction of a Sub-marine Vessel,” 1799¹

      Writing after the war from his home in Stamford, Connecticut, David Bushnell sent a lengthy letter to Thomas Jefferson on October 13, 1787, describing the “sub-marine vessel” used eleven years earlier in an attempt to sink the British flagship HMS Eagle, anchored in New York Harbor. The underwater attack was unsuccessful, as were two later attempts against British warships in the Hudson River. The history of Bushnell’s submarine and the creation and testing of a working replica can be found in the book by Roy R. Manstan and Frederic J. Frese, TURTLE: David Bushnell’s Revolutionary Vessel (2010), which includes a facsimile of Bushnell’s letter to Jefferson as published in the Transactions of the American Philosophical Society (1799).²

      The concept of submarine warfare has a long history, evolving in concert with the emergence of science and technology during the Age of Enlightenment of the seventeenth and early eighteenth centuries. In 1648, the Reverend John Wilkins, tutor and member of the Anglican clergy, published Mathematical Magick: or the Wonders that may be Performed by Mechanical Geometry. Wilkins’ goal was to show, by example, the application of mechanical principles to the many ideas that arose during the seventeenth century. He included a lengthy chapter: “Concerning the possibility of framing an Ark for submarine Navigation,” arguing “that such a contrivance is feasible, is beyond all question, because it hath been already experimented here in England by Cornelius Dreble [sic].”³

      Wilkins suggested several commercial and scientific applications, but made particular note of its military uses. “It may be of great advantage against a Navy of enemies, who by this means may be undermined in the water, and blown up. It may be of special use for the relief of any place that is besieged by water, to convey unto them invisible supplies …” then suggesting the possibility of clandestine operations: “… and so likewise the surprisal of any place that is accessible by water.”

      Wilkins was familiar with the vessel Cornelius Drebbel submerged in the Thames in 1623, with the intent to sell the concept to King James I. Although his idea never found favor within the English Admiralty, Drebbel did eventually receive funds from King Charles I to develop an underwater mine that he referred to as a “water petard,” used, albeit unsuccessfully, against the French in 1627.⁴ It is likely that Bushnell was familiar with Wilkins’ Mathematical Magick. Wilkins was a founding member of the Royal Society of London, and all of the publications of that society were available at Yale College when Bushnell entered as a freshman in the fall of 1771. Yet the submarine vessels Bushnell may have read about were fanciful concepts with little practical value.

      The story of submarine warfare, therefore, began in Connecticut at the onset of the Revolutionary War when David Bushnell conceived, built, launched, tested his submarine, and trained the vessel’s operators. The Turtle, a name bestowed by his friend Colonel David Humphreys⁵, was the world’s first undersea vessel designed and used specifically as a naval combatant. Bushnell lived during a time when inventive minds were being influenced by the expanding knowledge of science, then referred to as natural philosophy, being taught in universities throughout Europe and America. The “Principles” Bushnell was referring to in his letter to Jefferson—the “General Principles and Construction of a Sub-marine Vessel”—were based on the natural philosophy he soon became associated with when he entered Yale.

      When Nehemiah Strong (Yale, 1755) was hired to teach mathematics and natural philosophy in 1770, the college had made a commitment to provide students with the ability to concentrate their studies on subjects leading to careers other than the ministry. It was good timing for Bushnell whose interests were definitely secular.⁶

      War with England was almost a certainty, and Bushnell was determined to use his creative mind rather than a musket to support the revolutionary spirit growing in America. The library at Yale was filled with books by those natural philosophers—Isaac Newton, Robert Hooke, Robert Boyle, Edmund Halley and many more—their ideas appearing in the Transactions of the Royal Society, every volume of which could be found on the library shelves.

      In his letter to Jefferson, Bushnell referred to his propulsion system: “An oar, formed upon the principal of the screw, was fixed in the forepart of the vessel; its axis entered the vessel, and being turned one way, rowed the vessel forward, but being turned the other way rowed it backward; it was made to be turned by hand or foot.”⁷ An eye witness described it as: “a pair of oars fixed like the opposite arms of a windmill.”⁸ One of Bushnell’s textbooks, the Philosophia Britannica by Benjamin Martin (1747), devoted a section to windmill design, a significant power generation technology in the eighteenth century, and may have been the inspiration leading to Bushnell’s propeller.⁹ After the war, in 1785, Yale College president Ezra Stiles included Bushnell’s “Submarine Navigation by the Power of the Screw” in a list of notable inventions along with Benjamin Franklin’s “Electrical Pointed Rods.”¹⁰ What Stiles described as the power of the screw was Bushnell having created the first use of what is now referred to as a screw propeller—keeping in mind that the word “propeller” did not exist in 1776.

      Without any hope of an American navy capable of facing the world’s most formidable naval force, which was expected to soon arrive from over the horizon, Bushnell’s goal was to find another way to destroy a fearsome British man-of-war. The most vulnerable location of a ship’s hull was its nearly flat underbelly. Bushnell understood that because of the incompressibility of water, the destructive force of an explosion would be directed upward and into the flexible wooden planking. How to place a sufficient amount of gunpowder into a waterproof container; then covertly attach the container under a ship’s hull; and finally detonate the explosive charge were only a few of the technical problems Bushnell faced. Each of these goals was solved only with a combination of scientific knowledge, mechanical instincts and intuition, and a team of innovative and patriotic individuals.

      Bushnell experimented with explosives while at Yale and enlisted others in New Haven for help designing and building the parts for his submarine. Construction of the Turtle began at the family farm in Saybrook, partly in the hands of his brother, Ezra. The project was eventually moved to Ayers Point on the Connecticut River, where the Bushnell brothers, helped by artisans in the area, finished and tested his submarine, and where Ezra trained as its operator. Ready for action by the summer of 1776, the Turtle was carried down Long Island Sound and brought across land to the Hudson River. On September 6, the little wooden submarine was afloat at the southernmost tip of Manhattan, within sight of HMS Eagle.¹¹

      Although unsuccessful at sending Eagle to the bottom, Bushnell’s Turtle performed the rudimentary functions required of a submarine vessel. His ideas were a product of the age of enlightenment, yet it would take an industrial revolution to solve the inherent difficulties associated with propulsion, with underwater navigation, with providing an adequate air supply, and with placing an explosive device near, on, or into the targeted ship. The nineteenth century saw several attempts, most notably the sinking of the steam sloop USS Housatonic by the Confederate submarine Hunley in 1864. The Hunley, however, was also lost as a consequence of the attack. Technology had simply not advanced sufficiently by the Civil War to solve those same problems Bushnell faced, but it would not take long before that would happen.

      A hundred years after Bushnell launched his Turtle, Lieutenant Francis Barber, an instructor at the Navy Torpedo Station in Newport, Rhode Island, predicted the following: “The science of submarine navigation is likely to be one of great importance in connection with torpedo operations of future wars, both for attacking vessels and for entering harbors …”¹² Within a generation, “the science of submarine navigation” became a reality, as did Barber’s “future wars.”

      THE TWENTIETH CENTURY

      Warfare soon took a devastating turn, with unprecedented destruction and loss of life on the battlefields of Europe. Aircraft added to the lethality associated with technologies introduced to the

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