Washington's Spies

by Alexander Rose

  Making the telltale ink disappear would provide a hedge against discovery, which is precisely what Tallmadge set out to do. Quite by happy circumstance, a few months before, John Jay—about to become the new president of Congress—had enigmatically written to Washington about “a mode of correspondence, which may be of use, provided proper agents can be obtained. I have experienced its efficacy by a three years’ trial.”22

  Jay, a future coauthor of the Federalist Papers with Alexander Hamilton and James Madison, was referring to an extraordinary ink concocted by his older brother, Sir James Jay (1732–1815), a physician who had been living in London before the war. Sir James, knighted in 1763 by George III and described as “haughty, proud, overbearing, supercilious, pedantic, vain, and ambitious” (as well as being a notorious overcharge; his medical practice “became entirely confined among his own relations”), also happened to be a keen amateur chemist.23

  Many years after the Revolution, Sir James described to Thomas Jefferson that “when the affairs of America … threatened to issue in civil war [in 1775], it occurred to me that a fluid might possibly be discovered for invisible writing, which would elude the generally known means of detection, and yet could be rendered visible by a suitable counterpart. Sensible of the great advantages, both in a political and military line, which we might derive from such a mode of procuring and transmitting intelligence, I set about the work.” After “innumerable experiments, I succeeded to my wish.”

  Jay continues: “From England I sent to my brother John in New York, considerable quantities of these preparations.” Sir James himself turned spy when, using his ink, he “transmitted to America the first authentic account which Congress received, of the determination of the British Ministry to reduce the Colonies to unconditional submission.”24

  It took nearly six months for Washington to receive a small supply of what Sir James called a “sympathetic” ink, that is, “fluids by which if one writes on the whitest paper the letters immediately become invisible” but which are magically “rendered visible” by the application of a different chemical liquid. Technically speaking, the writing fluid is termed the agent, and the developer, the reagent (in Washington’s words, the “counterpart” or “counter liquor”).25

  Agent and reagent were difficult to produce, given the scarcity of the materials and the need for secrecy. When he moved back to America, Sir James brought a limited amount of the chemicals from England, but was eventually obliged, with Washington’s permission, to appropriate hospital supplies for his requirements.26 Between the two men, the ink was code-named “medicine,” and Jay would ship it to the general in a small doctor’s box. Even with the ingredients in hand, the ink was tricky to produce, for it “require[d] some assistance from chemistry” and, Jay reported, “I have no place where a little apparatus may be erected for preparing it” because “our house is so small, and so well inhabited, that there is not a corner left where a little brick furnace, which a mason could build in two hours time, can be placed.” However, “a log hut for the purpose might be soon run up, but it is also out of my power to effect this. Neither bricks, boards nor lime are to be purchased here, nor a carpenter nor mason to be had without great difficulty, if at all.”27 Jay soon got the help he needed, courtesy of Washington, for whom the ink was a priority. Colonel Udne Hay was commanded to supply “the assistance of a few artificers for a day or two to erect a small laboratory. As [Sir James] purposes making some experiments which may be of public utility and has already furnished me with some chymical preparations, from which I have derived considerable advantages I think it proper to gratify him.” And, added Washington, “should a few boards or such matters be wanting to complete the building which is to be of logs, you will also procure them, if it be in your power.”28 It was.

  For the most part, in the eighteenth century secret inks were rarely used. This was because they were generally based on organic liquids, such as the juice of leeks, oranges, limes, cabbage, and potatoes, as well as milk, vinegar, or urine (in a pinch). To develop them, the recipient applied heat, either by pressing the letter with an iron or holding a candle beneath it. The very simplicity of the revelatory process tended to outweigh the advantages bestowed by invisibility, which may have been one reason why the British—Clinton, in particular—preferred to write openly, so to speak, in cipher or by grille.

  Jay’s recipe, however, was revolutionary enough to amaze Washington. Performing his own experiments with the liquid, the general marveled that “fire which will bring lime juice, milk and other things of this kind to light, has no effect on it. A letter upon trivial matters of business, written in common ink, may be fitted with important intelligence which cannot be discovered without the counter part.” He soon dubbed this marvelous fluid the “sympathetic stain.”29

  So what was the “sympathetic stain”? Conducting tests on the Culper letters in the Washington collection at the Library of Congress is impossible, and even if performed would be unlikely to yield much of use owing to the age and brittleness of the surviving correspondence written in the stain. We can take a few stabs at what it could have been, using the few clues available.

  The Culpers tended to write on new paper, despite the added expense and the difficulty of acquiring it, in order to use the whitest available. Washington once advised, when he suggested that the Culpers could write in the blank leaves of books, that they should choose such volumes on the basis of “the goodness of the blank paper, as the ink is not easily legible, unless it is on paper of a good quality.”30 As a result—keeping in mind that the basis of sympathetic-ink alchemy is a change of color (if written in red, say, the developed message might appear in green) caused by the reaction between the agent and reagent—when Washington developed their letters, the Culpers’ writing appeared in the hoped-for black. Only by “wetting the paper with a fine brush” dipped in the reagent, specified Washington, could one render the writing visible.31 Another clue is that Jay conducted “innumerable experiments” (as he said in his letter to Jefferson) to get the compounds and sequence right, so the solution could not be an obvious one. Nor were the ingredients easy to come by, since Jay needed to get the key chemicals from a hospital or dispensary. And finally, as Washington found, the ink was impervious to heat.

  There are some five hundred known sympathetic-ink formulas, and no doubt many hundreds more could be concocted. The vast majority of these can be discarded, as they fail at least one of the above criteria, and in any case, at that time there were but three types of sympathetic inks known. There is one that does fulfill every requirement. Mix and dissolve 60 grains of gallic acid with 10 grains of powdered acacia, more commonly known as gum arabic. (Gallic acid is a colorless or slightly yellowish crystalline acid derived from gallnuts, primarily Chinese in origin and so hard to find except in hospitals, where they were used by eighteenth-century doctors as an antidiarrheal medication.) After several attempts, you should have a solution the color of pale straw. For the reagent, acquire 30 grains of ferrous sulphate and dissolve them in 8 ounces of distilled water, thereby producing a colorless developer. The reason why Washington specified using a “fine brush” to reveal the message is that the reagent has a tendency to smear the text if too much is swabbed over it. Once the “counter liquor” is properly applied, the writing will gradually appear, tinted a pale greenish or bluish black, but will eventually, with exposure to air, turn coal-black. The document itself will, thanks to the oxidation of the ferrous salts, turn slightly brownish, as indeed the Culper letters often are.32

  In mid-April 1779, Woodhull finally received “a vial for a purpose that gives me great satisfaction” and immediately began using it.33 Even so, it took a year to procure sufficient supplies. The Culpers, as a result, often found themselves grievously short, and Washington himself tended to write openly to Tallmadge to preserve the precious drops. When, however, Woodhull finally had enough of the ink, he tended to hoard it for fear of another shortage, leading Washington to remark crossly t
o Tallmadge that “what I have sent for him at different times would have wrote fifty times what I have recd. from him.”34

  Armed now with his sympathetic stain, Washington soon began to cast round for a permanent New York agent so that Woodhull could hold the fort in Setauket. His eye settled on Lewis Pintard, a merchant who had been appointed (with General Howe’s acquiescence) in early 1777 as commissary to American prisoners in New York, his job being to ensure they received proper care. In his letter asking for Howe’s permission to keep an American representative in the city, Washington had pledged that Pintard was “under parole to transmit no intelligence.” By the late spring of 1779, he had evidently decided that Pintard was too valuable an asset to let lie fallow.35

  On May 3, 1779, Washington sounded out Elias Boudinot, his commissary-general of prisoners. “It is a matter of great importance to have early and good intelligence of the enemy’s strength and motions, and as far as possible, designs, and to obtain them through different channels. Do you think it practicable to come at these by means of P——d? I shall not press it upon him; but you must be sensible that to obtain intelligence from a man of observation near the head quarters of an army from whence all orders flow and every thing originates must be a most desirable thing.” If Pintard were willing, he would “entitle himself not only to thanks but reward, at a proper season.” Understandably, Pintard would be concerned about exposure—the British no doubt steamed open his dispatches to headquarters—but Washington alluded to the possibility of using his new weapon, the ink, to evade their snares. The general asked Boudinot “to hint the matter to the person mentioned, for trial of his willingness to engage in a correspondence of this kind.”36

  Nothing came of the scheme: A miffed and insulted Pintard refused to send any reports to Washington. Some time later, he gave his reasons when he complained of the “disagreeable circumstances attending my particular situation” that had “exposed me to the most dangerous … consequences imaginable.” Pintard was too discreet to mention Washington’s approach, but word had somehow leaked out and he was “considered as a person of the most dangerous principles to the safety of the City, as a spy and common enemy of the British Government.” As he was “extremely unhappy,” Pintard asked Washington to appoint “some other person … to take charge of the American prisoners in New York” so he could “retire to my farm.”37 (He later became Washington’s wine supplier.)38

  Despite his faux pas, Washington wasn’t yet willing to give up his quest for a New York agent-in-place. On June 27, 1779, Washington suggested to Tallmadge, then stationed in Connecticut, that he make contact with “a man on York Island [Manhattan], living on or near the North River, of the name of George Higday who I am told hath given signal proofs of his attachment to us, and at the same time stands well with the enemy.” This Higday had, the previous month, helped three stranded American officers cross the Hudson into New Jersey and they had cited him as a potentially useful friendly.39

  A week later—on July 2—Colonel Banastre Tarleton, leading a two-hundred-man force comprised of part of his British Legion, the crack Seventh Light Dragoons, the Queen’s Rangers, and the Hussars, struck Tallmadge’s camp at about five in the morning. Sabers fiercely clanged, and the raiders were eventually repulsed with the help of the local militia, but not before the dragoons had suffered ten casualties and eight men captured, along with twelve horses taken—including Tallmadge’s charger, whose saddlebags had contained twenty guineas from Washington intended for Woodhull and, worse, his letter of June 27 mentioning George Higday’s name and location.40

  Tallmadge was mystified by the attack: How had the British known exactly where to find him, and why had they undertaken such a risky operation? What he did not know was that a June 13 letter—not written in the stain—from Washington to Tallmadge that mentioned “C——r” and a “liquid” he was using had been intercepted by the British, who decided to venture capturing Tallmadge himself.41

  Washington was composed, but was certainly annoyed at what he regarded as Tallmadge’s carelessness. “The loss of your papers was certainly a most unlucky accident and shows how dangerous it is to keep papers of any consequence at an advanced post. I beg you will take care to guard against the like in future. If you will send me a trusty person I will replace the guineas.” However, “the person most endangered by the acquisition of your letter is one Higday, who lives not far from the Bowery, in the Island of New York. I wish you could endeavour to give him the speediest notice of what has happened. My anxiety on his account is great.”42

  His chiding was not altogether warranted. It had been Washington, after all, who had blundered badly in using Higday’s real name, not Tallmadge. Though the plot to nab Tallmadge had been thwarted, the British couldn’t believe their luck in intercepting a second letter from the commander-in-chief, and it was read at the highest levels—by Clinton himself. To make matters worse, the June 27 letter had also mentioned “C——r”—so now the enemy had a double confirmation that not only was there an active agent by that alias, but that Tallmadge was head of the intelligence service and was probably operating a ring on Long Island, through Connecticut, and across the Sound.

  They could deal with this C——r later. On July 13, troopers broke down Higday’s door and arrested him. Terrified for his life, and either convinced already, or persuaded by his interrogators, that Washington had had the letter deliberately intercepted to destroy him, Higday wrote a semiliterate, pathetic confession from prison to Clinton. After he had helped the officers across the Hudson, they said “what a fine thing it might be for me to fetch information over for Washington” and “that he would make me rich in so doing.” Granted an audience with Washington, Higday offered his services for pay, and the general agreed to give him some money. Higday’s modest intention had been to buy a cow with his wages, but Washington’s money turned out to be counterfeit and Higday refused to work anymore. He assumed Washington had put his name “in the black book” and betrayed him out of spite.43

  It’s unlikely Higday was executed, because Clinton, as he told his sisters, was a forgiving man, especially to such confused and harmless small fish as Higday. “From good policy and perhaps a little more feeling than is usual for those in my situation … I have never executed a spy.” Why? Because “I have made good use of them by employing them double”—a sentiment belying his self-regarding virtuousness.44 Indeed, Clinton may have tried to recruit Higday as a “double,” but he was useless, for Washington knew he had been compromised. A victim of the spy game, poor Higday went back to his little place on the Bowery and endeavored to disappear.

  The Higday gaffe did at least demonstrate to Washington and Tallmadge the urgent need to encipher their letters. Given the chronic shortage of invisible ink, Tallmadge vowed never to allow his agents again to be placed in such danger, and set himself the task of creating a code that would serve as an additional hedge against discovery.

  Inventing a workable code from scratch is a tall order. Today’s cryptographers (those who create codes, as opposed to cryptanalysts, who break them) are fortunate enough to work for intelligence agencies able to draw on many decades of institutional experience. Tallmadge had no such luck. He lacked instruction manuals, professional advice, and even knowledge of which words to include. The code he eventually conceived may have been simple but it was not a bad one. Though it certainly wasn’t up to the cutting-edge standards used by European diplomatic codemakers, Tallmadge was not obliged to shield his men from European diplomatic codebreakers. So long as it frustrated a casual reader, it would suffice.

  His code was a distant descendant of the Ave Maria cipher created by a priest, Johannes Trithemius, author of the first book printed on the subject, the Polygraphiae of 1518.45 (Men of the cloth made superb cryptographers owing to their ability to translate Hebrew, Greek, and Latin back and forth.) Trithemius constructed a table pairing the twenty-four “plaintext” letters of the alphabet with a selection of nouns, verbs, adjectives,
and adverbs. The sender would substitute one of these corresponding words for each letter of the plaintext message to form a coherent prayer—hence Ave Maria. I’ve reproduced a partial example below for the letters A through D:

  So, if we wanted to encipher “Abbas Trithemius,” we would select “Deus” from the A row of the first column, then “clementissimus” from the B row of the second column, then “regens” from the next B row in the third column, and “celos” from the last column and so on. The Latin prayer of “Abbas Trithemius” would emerge as (once some “nulls,” which don’t mean anything and can serve as red herrings, and “joiners” to make the sentences intelligible, which I’ve italicized, were added): “Deus clementissimus regens celos manifestet optantibus lucem seraphicam cum omnibus dilectis suis in perpetuum amen suauitas potentissimi motoris deuotis semper vbique.”46

  Trithemius’s cipher was clever but laborious, as it used an entire word to replace a single letter. A simple sentence could translate into a page-long prayer—suspiciously lengthy even for the most theologically fervent. It never really took off. Europe’s few cryptographers instead relied on a French code system, also dating from the Renaissance, known as a one-part nomenclator.

  For this, a codemaker compiled two parallel lists, the first containing plaintext words and the second, numerals in ascending order. Thus, “apple” might be represented by the number 9, and “meeting” by 256, “thunder” by 407, and so on all the way through to “zoo” at 522. Instead of writing words, the cryptographer substitutes a number, so that eventually the message appears as a series of digits separated by periods.

  A one-parter does contain a major flaw that only gradually emerged: All words alphabetically between “apple” and “meeting” must necessarily bear numbers between 9 and 256. Given that the science of determining how frequently certain words, bigrams, and letters occurred was in its infancy (in English, for instance, “the” occurs 420 times in every 10,000 words, the bigram “th” 168 times in every 1,000 words, and “e” 591 times in 1,000 words), an observant cryptanalyst would notice a “bunching” of numbers around particular points.47 Once he had three or four messages in his possession, and having verified that the numerals petered out at about 520, our cryptanalyst could hypothesize that the flurry of code numbers hovering around the 400 mark—or four-fifths of the way through the series—was signaling a frequently used word, probably beginning with “t” and therefore almost definitely “the.” Likewise, a bunching in the single digits pointed a finger at the word “a,” and in the mid-100s, “from,” and in the low 500s, “which.” From there, it was a matter of attrition to crack the code; i.e., “of” must be somewhere between 256 and 407, and most likely around the early 300s, so he would start looking for the telltale bunching in that area. Once this basic structure had been established, the cryptanalyst would scour for common military and diplomatic terms: “ambassador,” “king,” “army,” and so on. Sooner or later, the pieces would fall into place.