Navigating on Paper at Sea

The information recorded in the logbook is, first, a record of the crew's attempt to find their way from their departure to their destination while preserving life and property. While the specific methods for doing so varied somewhat over time, all logbooks contain some common information, laid out in similar fashion, toward this end. They all divide the ship's day into one- or two-hour increments, from noon to noon, as the keeping of time on board, like most other aspects of life, differed from the way it was done ashore. Ships operated twenty-four hours a day; the measuring of work time and passage time reflected that. Noon was the moment when the ship was directly underneath the sun; by establishing that moment with a sighting instrument, the master could easily work out the ship's latitude—how far the ship was north or south of the equator. Expressed in degrees between zero and ninety, that latitude would be recorded in the log. If the sun was obscured at noon, the master might record a sighting of the sun at another time during the day, or of one or more stars at dawn or dusk, when the horizon was visible. Those sightings required more calculations, but a fully-qualified navigator would know how to perform them.

The rest of the day-to-day navigation of the vessel was conducted by a set of techniques collectively known as “dead reckoning,” from “ded.” or “deduced” reckoning. Deduced reckoning may sound like an educated guess; it was. The basic principle was that keeping up with the vessel's speed, compass course, and elapsed time since departing a known position would provide an updated position. In theory that is true, but in practice, the wind, the sea, the earth's magnetic field, and human fallibility introduced too much error into this “reckoning” for it to be any more than an estimate of position, and this error was compounded the longer the vessel sailed away from that initial known position. So, the “DR,” as it was usually noted, would be corrected by “observation”—whether that meant the noon sun sight, a sighting of another celestial body, or the distance and bearing of a known landmark. Navigators also applied corrections based on their apprehension of current, leeway (the side-setting of the vessel by the wind and sea), known or suspected errors in the reported compass courses steered by the helmsmen, and variation—the difference between magnetic north and true north, measured as an angle, which itself varied by location on the earth's surface.

With no widely available means of determining longitude with any accuracy, the DR would provide an estimated longitude to go along with the observed latitude; one requires both a vertical and a horizontal point to establish a fixed position on the earth's surface—otherwise, one has only a line of position.Footnote ³ Needless to say, the estimated longitude was not nearly as trustworthy as the observed latitude—and every navigator knew that.

The caution engendered by the lack of faith in estimated longitude is evident in the logbooks. When the master believed he was approaching any land, including his intended destination, he grew cautious. He slowed the vessel down by taking off sail. Sometimes he tacked or wore ship—put the vessel through the wind, zig-zagging back and forth—or he “lay to”—put a little bit of sail against a hard-over helm, so the vessel did nothing but scallop slowly along, like a duck with her head under her wing.Footnote ⁴ He might do this, even in good weather, if it would help him avoid closing with the coast at night, when he could not see ahead. This gave him the time to take soundings—cast a lead line to determine if they were coming into shallower water, and if so, what the bottom composition was, which could help tell him where they were, especially how close to shore. The cautions masters took when approaching their destinations, largely out of awareness of the likely error of longitude in their logs, set a trap for historians trying to determine trends in vessel passage speeds over time; how fast the vessel completed a passage, from departure to entering the destination port, was not the same as how fast she could travel through the water.Footnote ⁵

A vessel could be carried along, or set off her intended course, by a current, but her ability to reach her destination in a timely manner was entirely dependent on the wind, so it is natural enough that the direction and speed of the wind, in the context of general weather conditions, take up so much space in a logbook. We find, in the narrow columns on the left-hand side, wind directions next to courses steered. In the Remarks column, on the right-hand side, only an event of most unusual import could usurp the otherwise-universal place of weather conditions as the first, and most frequent, notations. If we are lucky, we also find frequent records of sail changes associated with changes in wind direction and strength.

One cannot overstate the violence of heavy weather at sea on a sailing vessel of modest size. In the North Atlantic, a vessel making a transoceanic passage could expect to encounter such conditions. From late autumn to spring, there might well have been as much violent weather as moderate. The labour required to work the vessel in such conditions is something we moderns can only dimly imagine. Yet, such labour was all in a day's work for an average North Atlantic sailor, who did it over and over again, carrying out the master's orders to put this up or take that down, tie a reef in that sail or let one out of another. The Remarks column routinely records broken spars, split sails, parted control lines, and worse damage. Occasionally, a man would fall or slip overboard. The crew might see him go under, or lose sight of him first. The event would be recorded in Remarks.

“NOTD”: Reading More into the Logbooks

The acronym “NOTD,” occurring twice in the log kept aboard the snow George, means, I believe, “nothing occurred this day.” That, of course, is not literally true; it reminds us that, like any written document, the log contains what its author deemed important enough to include. Excluded by that filter will almost surely be twenty-four hours’ worth of interaction and communication between crew members, routine minor adjustments of sail trim (and some major ones), and the interior monologues and free-associative ruminations rightfully beloved of novelists. I added the qualifier “almost” before “surely” because no two logs are alike, and the idiosyncrasies of individual authors vary enough that predicting with certainty what will and will not be found in a given log is impossible. That is one of the compelling aspects of these sources. Fortunately, much that is routine and mundane does find its way into the logbooks. Anything the master or another supervisor has assigned to a group of sailors will likely appear, in a form such as: “People employed making matts” or “People employed scraping the sides.” Because log authors typically include large work tasks, as well as incidents of damage, an intact logbook provides a useful maintenance and repair record for the period of time it covers.

It also tells us some things about the crew, although what it does not say is as important as what it does. Historians are accustomed to finding rich source material in legal case records, keeping in mind that legal case records exist only when something is amiss; if everything goes smoothly and everyone is happy, there are no lawsuits. On board ship, if everything is going smoothly and everyone is reasonably happy, the best indication of that is either blank space or something to the effect of “People employed variously.” On the other hand, if there is personnel trouble, it will be recorded, unless it is a private matter between crew members that does not reach the attention of the log's author. Discipline and desertions are routinely recorded, along with, in most cases, some indication of the circumstances surrounding them—though a desertion may well be succinctly recorded with no further elaboration: “Robert Jenkins ran.”

As a log's author was a person at the top of the ship's hierarchy—a master, commander, or supercargo—his Remarks on interactions with other people will also include those with business and official contacts, such as agents and merchants in both home and destination ports, other ship's officers and crew with whom he might have contact, customs officials, and lawyers.Footnote ⁶ Much of this content provides only clues that prompt the researcher to investigate further: “Dined with Mr. Carroll at his home.” Who is Mr. Carroll? What was the relationship between the two?

Again, it is worth keeping in mind that what we think is important and what the author thought was important may or may not coincide. In neither the master's nor commander's logs for July 1770 is there any mention of both men from Sultana having dined ashore with a gentleman in Virginia. The only way we know it happened is from the gentleman's—George Washington's—day diary.Footnote ⁷

Aside from the human world and the immediate concerns of the weather, logs do occasionally include information about the nonhuman marine world. The log kept aboard George mentions a red tide off the coast of Ireland, and that same log contains several mentions of encounters with sea creatures, most of which were fatal—for the sea creatures. Mentions of marine animals provide just as stark a reminder of cultural difference between then and now as records of floggings and enslavement. Dolphins, other porpoises, and sea turtles were, to them, sources of fresh food, and pursued as such. The author of the George's log lists the specific internal organs of a harpooned porpoise that he found particularly tasty.

Cultural differences across time also play out in descriptions of ports of call or passing scenery. As the George arrived in the Leeward Islands in late May 1806, the log's author recorded the following observation:

The author lived in a world where the brutal and dehumanising regime of plantation slave labour was a normal part of the colonial landscape. It is not surprising, then, that he did not feel the need to express any opprobrium about that; indeed, in a few weeks, he would agree to take thirty enslaved persons from St. Thomas to Campeche as human freight.

Cracking the Code: Deciphering the Eighteenth-Century Atlantic Logbook

A key to the shorthand found in a logbook is accessible, though the historian's ability to comprehend the navigation recorded there will depend to a large extent on that person's technical expertise. The importance of such technical expertise to the history of navigation has been noted in scholarly journals; without it, one cannot, for example, reconstruct the voyages of a vessel adequately enough to plot them, or make informed judgements about adjusting such plots for obvious errors in the original source.Footnote ⁸

Logs vary somewhat in content and format, but not dramatically. I have worked with both merchant and Royal Navy logbooks; significant differences were limited to content in Remarks specific to their respective activities. As noted, the most basic division of each day's entry may be considered “left-hand” and “right-hand”—the left-hand side being the information necessary to construct the DR for the day, given in one- or two-hour increments, and the right-hand side being the Remarks column. Below both is a horizontal row for recording the summary navigational data for the whole day. Without further ado, here is a transcription of one page of the George logbook, formatted exactly like the original (see Figure 1).Footnote ⁹

Figure 1. Transcription of a page from the George (ship) logbook 1805–1806, Am .6823, Historical Society of Pennsylvania, p. 66.

Taking the left-hand side first, we have abbreviated column headings standing for Hour, Knots, Half-Knots. Since the nautical day begins at noon, the first “2” here is 1400, or 2:00 p.m. (“p.m.” stands for “post-meridian,” or “after noon”). The middle “12” is midnight, and the final one is noon, which ends the day and begins the following. “Knots” is nautical miles per hour. While we would express “three-and-a-half knots” as “3.5,” they were less inclined to use decimals in general; this can in fact be misleading, because what looks like a decimal, as in the “16.57” Lat by Ob entry in the top section of this excerpt, is actually just one of an assortment of punctuation marks, used seemingly at random, to separate the first pair of numbers from the last. Indeed, it is common to see no such punctuation at all; a space serves the same purpose.

This is a good place to point out the rampant inconsistency of eighteenth-century writing. Sometimes it seems as if the author is being inconsistent on purpose; would it not be easier to get in the habit of using the same mark for the same purpose? They did not. Nor can the researcher assume that the same mark in one place means the same thing as it does in another. A good example is the use, in the above excerpt, of quotation marks or ditto marks in the “HK” column. Ditto marks were already in use by this time, so it was reasonable for me to assume that the author was using these as such. It was only by adding up the distances for the day both ways—one, assuming these were ditto marks; and two, assuming they meant “0”—that I could determine that, actually, they meant “0.” I performed those computations on several examples to make sure the author was, indeed, being consistent.

The double-dashes, which I transcribed as written, may be inferred to be ditto marks; in the Courses and Winds columns, that is the only interpretation that makes any sense. I would never assume that another log author would employ the same marks the same way. It would be necessary to test any and all inferences as best I could.

Courses and Winds are expressed using the 128-point compass, and that is one consistency of eighteenth-century logs. Courses here are courses by the compass, uncorrected. They are expressed as a direction toward which the vessel is steered. Winds are expressed as the direction from which the wind is blowing. A vessel with a compass course of NW (northwest) is being steered toward the northwest, or roughly three hundred fifteen degrees on the 360-degree compass. A NW wind is one coming from that direction.

In our own time, we use the 360-degree compass. They used a compass divided into “points.” A point, for reference, is 11.25 degrees. In the excerpt above, “ESE” means East Southeast, and “W by S” means West by South. Trained on the 360-degree compass from an early age, I find it helpful to convert these directions to the system with which I am familiar. It is likely that some experts find this unnecessary; that would save time and effort. However, an advantage of degrees (expressed in decimal format, rather than degrees-minutes-seconds) has the advantage of allowing for calculations, especially automatic ones, such as those Microsoft Excel can perform. For conversion, I use a table in Wikipedia.Footnote ¹⁰ Occasionally, I have found an error in the original log when it records a direction in this system that is not to be found anywhere in the table. Context is helpful for correcting those.

Once I have both course direction and wind direction for a given time increment, I can make a close estimation of the point of sail—the angle the vessel is sailing to the wind. Even for those not interested in analysing sailing performance, a general understanding of this concept is necessary for grasping the limitations and imperatives of sail power, and thus the structure of the voyage itself. As a general rule, it was difficult for any eighteenth-century commercial or naval vessel to sail any closer to the wind direction than forty-five degrees, and sailing that close tended to be an uncomfortable business, with wind-driven seas hitting the bow of the vessel and the wind creating maximum heeling—leaning—force in the sails, and maximum leeway—side-slippage—through the water. Sailing close to the wind also reduced the vessel's speed from what it would be with a greater angle, and increased the danger of being taken aback in a sudden wind shift; with the sails trimmed as close to the wind direction as they could be and still fill, a small wind shift could put that wind on the other side of those sails, back-filling them and stopping forward progress. Without momentum to move water past the hull and rudder, a sailing vessel will not respond to her helm; she is temporarily out of control. Being taken aback was also likely to cause shock-induced rig damage.

Sailing vessels preferred, then, to sail downwind if at all possible, sailing upwind only when necessary. The ability to sail into the wind was, indeed, necessary for manoeuvring in tight quarters and avoiding dangers such as a lee (downwind) shore or reefs, but it was an exhausting and slow way to make passage. Thus, all the favoured ocean sailing routes offered consistent downwind sailing. In the Atlantic, that meant the prevailing westerlies, curving eastward from the northeast coast of North America toward northern Europe; and the Trade Winds, offering steady and sufficient propulsion from the west coast of Africa to the Caribbean. The Atlantic is naturally traversed in a clockwise direction by wind-powered vessels. Sailing from northern Europe to New England, then, as Sultana did in the late summer and early autumn of 1768, was a “wrong-way” passage, requiring sustained upwind sailing against the prevailing weather in the North Atlantic. That is why her westward passage took twice as long as her later eastward return.

Masters thus had to make sailing decisions that took into account the impossibility of sailing too close to the wind, and the desirability of sailing at an angle to it of at least 90 degrees but preferably short of 180, at which point the vessel's speed would drop somewhat, as some sails were shadowed by those behind, and the vessel took on some amount of a corkscrewing motion notorious for inducing nausea, a word that shares its root with “nautical.” Running dead downwind, like sailing close upwind, also exposed the vessel to the chance of having the wind suddenly shift to the other side of the sails, transmitting a shock to the rig. In a severe storm, however, this point of sail was a common survival tactic, when no other options remained. In such cases, however, the vessel would likely have no sail up, and be running “under bare poles.”

The Remarks Column: Details and Valuable Incidentals

With some understanding of the physical imperatives dictating the course of the voyage, the researcher is better equipped to understand what is recorded in the Remarks column to the right—a feature universal in eighteenth-century logs, both commercial and naval. The first important ingredient here is the weather; the terminology they used is not what we use now.

The Bottom Lines: Understanding the Day's Navigational Data

In the later section on plotting a voyage, I will explain how the daily navigational data entries are derived, and how to estimate them if they are missing. Here, I will explain what they mean.

The “Course” entered at the bottom left of the George's log excerpt is based on all the courses steered that were recorded for the day, but corrected for variation, leeway, and any other factors of deviation the master may have deemed relevant. The “Dist” (Distance) here is the total distance run in the twenty-four hour period, in nautical miles. “Depar” (also sometimes abbreviated “Dep”) is Departure, which is one leg of the basic navigational right triangle. “Dif lat” means difference in latitude, and records the difference between the navigator's best estimate of yesterday's latitude and today's. “Lat by DR” means latitude by dead reckoning, which is calculated using the data recorded in the upper left-hand side of the day's entry. “Lat by Ob,” on the other hand, is latitude calculated from either a celestial sight or a bearing and distance from a known fixed object. It is thus more reliable than Lat by DR. Any difference between the two is a good indication to the navigator of the error in his DR.

The next three entries have to do with estimating longitude which, as discussed, was far less reliable than estimating latitude. “Mer dist” means meridian distance, and it is a running total of the nautical miles of longitude run. That means that when the longitudinal direction reverses, such as from west to east, the number moves in the other direction too. “Lon made” is the difference, in degrees and minutes, between the estimated longitude for the day before and that of the current day. “Lon in,” or longitude in, is the estimated longitude, again in degrees and minutes (a degree contains sixty minutes; a minute contains sixty seconds). As noted, there is no consistency in the use of punctuation to differentiate degrees from minutes. It may be a period: 2.59; a dash: 2–59; a comma: 2,59; double comma: 2,,59; or a space: 2 59. The entry right next to it may employ a different mark. In the George/Reward logbook, this is all seemingly random. Finally, we have “B & Dist,” bearing and distance, for use when such a desirable line of position was obtainable.

The reader will notice, however, that on the first day of the excerpt above, only one of these items—Lat by Ob—is recorded; and on the second day, none are. This is why I had to reconstruct all that data from the information in the other parts of the log. More on that in the section on plotting a voyage.

Commercial Versus Naval Logbooks

I have not worked with naval logbooks from vessels in active combat; that is outside my purview of interest. I will speak to those I have worked with: those of His Majesty's Schooner Sultana, working in dispatch and customs enforcement on the North American Station 1768—1772. As was standard on naval vessels, Sultana had a commander—the commissioned officer in charge of carrying out her orders—and a master and pilot, a warrant officer in charge of her sailing operation and day-to-day navigation. Both of their logs survive in their entirety. They are similar, though the master's log contains somewhat more sailing details than the commander's. I should note that the logs do not always agree; it is obvious that one was not copied from the other, and their points of divergence, though minor, offer the researcher the opportunity (and obligation) to think about why such differences might exist, and where errors or differences of judgement may lie.

The Royal Navy was easily one of the largest and most complex bureaucracies on earth, and its policies and procedures were unusually standardised for the time. Muster books, in which commanders recorded who was on board, and in what capacity, as well as who had deserted and who owed what for items purchased from the ship's stores, were preprinted with the lines and column headings. These records, invaluable in themselves, were sent ashore to be checked by those responsible for the Navy's accounts. On the other hand, the logbooks of Sultana's master and of her commander were, like those of George/Reward, drawn by hand. The navigational data for the day was all combined on one row on the left-hand side, with Remarks taking up the right-hand side, as with the mercantile log.

The Perennial Challenge of Transcription

The primary challenge in interpreting the log of Sultana's master and pilot, David Bruce, was transcription. Reflecting the social-class differences of commissioned versus warrant officers in the Navy, Lieutenant Inglis, the commander, was obviously literate; his biographer tells us that he attended the Philadelphia school that eventually became the University of Pennsylvania.Footnote ¹¹ Bruce, on the other hand, was barely literate, relying largely on phonetic spelling, as was so typical of non-elites in the eighteenth century; in all probability a Scot, he struggled with the place names of North America, largely corruptions of indigenous words, and ships named for Greek gods and Biblical Hebrews. His handwriting was terrible, probably exacerbated by the hurriedness with which he had to make his entries, and perhaps too by the motion of the little vessel. Merely reading and understanding the log required a much greater investment of time and effort than would be required for reading something of the same length and scope of content written in clear modern English. However, experience has convinced me that the process of careful transcription yields benefits beyond the extraction of concrete information from the source. In attempting to interpret place names, the names of other ships, and even standard nautical terms that were difficult to make out, I learned, much more thoroughly, the world in which Bruce was writing his log. I had help with this; a native English mariner helped me with landmarks along the south coast of England, used by Bruce and Inglis—and countless other mariners—to pilot the English Channel.Footnote ¹² That, in turn, allowed me to follow their route on a chart, and check my plot against the bearings and distances recorded to those places in the logs. My need for expert help there brings up another important point about transcription: it is a difficult task to do well in the absence of some prior expertise in the subject matter. Someone not already familiar with nautical terminology, with the basic concepts of piloting, navigation, and operation, would be hard-pressed to read one of these logs; whereas someone equipped with such understanding is in a good position to solve puzzling bits of handwriting using context. As with transcription in general, a familiarity with the grammatical conventions and punctuation habits (such as they were) typical of the time and place also helps.

I am firmly convinced that to extract full value from one of these logbooks requires commitment to transcription. The researcher who has to type out what the log says, word for word, cannot avoid all the judgement calls required in any transcription; and thus cannot avoid finding out what is not immediately apparent. That is true whether or not the researcher has any interest in using the navigational data in the log to reconstruct a voyage.

Plotting Atlantic Voyages from Eighteenth-Century Logbooks

An important component of the GSR database project, as other articles in this issue make clear, is the plotting of the voyages recorded in the logbooks. Any sort of step-by-step guide to that process would be a full-length article in itself; here, I will note some important considerations, and what this process contributes to understanding the eighteenth-century human Atlantic.

First, the obstacles: even with the benefit of a logbook containing full navigational data, the researcher's judgement will be called upon constantly, as with transcription. With Sultana, not only did I have one logbook with complete data; I had two. Still, plotting the schooner's passage out of the English Channel and into the Atlantic to begin her westward crossing, adhering faithfully to the positions recorded, put her on land in northwest France. That, obviously, was impossible. Where is the error? Is that even possible to determine after the fact? In this instance, it was not. This forces us to think about how masters and commanders used these logs; what faith did they routinely place in their own reckonings and observations, and how did they guard against falling victim to potentially fatal error? In this case, there is no mention in the logs of straying dangerously close to the French coast; it is safe to assume that the schooner tacked her way out of the channel with no close calls. My judgement call was to move the plotted track north and westward; and to think about why that was necessary. We know that, unfortunately, navigational errors did indeed lead to disaster. I found many instances in Sultana's logs where Bruce's and Inglis's recorded positions did not agree; both could not be correct. Sometimes, the Remarks column provided clues, such as mention of an off-setting current and the correction made to the DR accordingly.

With the log of the George/Reward, as is obvious in the excerpt included above, most of the summary navigational data was left out much of the time. The author of this log was a supercargo, not the master, and therefore this was not the primary navigational log of either vessel.Footnote ¹³ It is, however, what we have; to plot the voyages contained therein, I had to determine a way to reconstruct them, using the information at hand.

I was trained in modern piloting and navigation, not eighteenth-century piloting and navigation. Basic concepts convey, but basic techniques differ. I had to consult secondary sources to interpret the summary data column headings, and to learn indispensable facts, such as that the courses recorded throughout the day were compass courses, whereas the course-made-good—the course recorded at the bottom, for the entire day—was corrected for variation.Footnote ¹⁴ Variation—the difference between the direction of the magnetic north pole and the geographic North Pole—can be over twenty degrees in the North Atlantic; failing to account for it could put the vessel's estimated position so far off as to be useless. It also changes as the vessel's position changes, so the correct estimated value must be looked up using an estimated position. Fortunately, the U. S. National Oceanic and Atmospheric Administration maintains an online calculator using a model dating back to 1590.Footnote ¹⁵

Through trial and error to determine what yielded plausible answers, and comparison with examples mentioned in secondary sources, I was able to determine that the method used in this logbook was “plane sailing”—computing position each day using the plane right triangle. This is simple to visualise: for every shift in position from one place to another, regardless of the direction of travel, there is a vertical and horizontal component; the vessel moves up and over, or down and over. Those two components form the two straight legs of a right triangle—a triangle in which those two legs form a ninety-degree angle. The hypotenuse—the diagonal line connecting the two straight legs—is the distance travelled on the course-made-good (expressed as an angle). While it is true that the surface of the Earth is curved, not flat, the error introduced by assuming a plane rather than a spherical triangle is too small to be significant as long as distances are limited to a few hundred miles. Since an eighteenth-century sailing vessel was doing well to make more than a hundred miles a day, that was not a problem. The basic trigonometric functions, then, could solve the triangle, allowing for the combining of the various courses steered throughout the day into one average course-made-good, and the adding-up of the distances for each leg by multiplying the knots (nautical miles per hour) by the number of hours (two, in this log). This provided the values needed to use those trigonometric functions. In the eighteenth century, tables of those solutions—called traverse tables—were carried aboard. With a modern computer at hand, though, I set up auto-calculations in an Excel spreadsheet, after consulting my own set of traverse tables as an orienting reference.Footnote ¹⁶

Generating the data I needed to reconstruct the George/Reward voyages took three weeks of full-time, mentally exhausting work, and I may never repeat the exercise; it reminds me of carefully crafting a set of moulds for a fibreglass boat, and then only using them to make one hull. That analogy fails, however, when I consider what I learned about how the daily navigation of these ordinary trading vessels worked. I had to make the calculations myself, and evaluate their reliability. I had to compare them with those from the sections of the log where the original author provided them. When I finally got to the point where I could plot the voyages, the obvious errors revealed a situation more complex than simply my work being wrong: the voyage for which the author provided full data put the vessel at least one hundred miles too far west toward the end of the voyage, and I had to think about why that was. My own plot, from Jamaica to New York, looked good until the Reward turned northeast after coming out of the Yucatan Passage around the west end of Cuba; it then turned north too early, sending the vessel across the Florida peninsula, and, while moving over open water again, turned west too early, with the final position in the mountains of West Virginia. Only with these plots laid out on the chart could I begin to compare them with what the currents were likely doing to create growing divergence between estimated and actual position. Only then could I see for myself how dangerous the inability to accurately fix longitude could be to these vessels and their crews. Yet the Reward did not crash into Florida or Maryland's Eastern Shore, just as Sultana did not crash into Brittany. The masters knew what they were doing; they knew how much to trust what they wrote down in the log, and how much to trust what they did not. Unfortunately for us, what they did not record in the log is what we as researchers have to learn about their navigation. As Willem Mörzer Bruyns argued, advancing the history of navigation requires the acquisition of technical expertise on the part of historians of navigation.Footnote ¹⁷

Analysing Sailing Performance and Operation

Mining a logbook for insight into eighteenth-century navigational practice requires the acquisition of some technical expertise. Mining one for insight into operating an ordinary period sailing vessel requires the same thing. In my experience, such an effort proceeds in three stages. First, the researcher goes into the logbook with a working knowledge of how these vessels worked. This is not the knowledge of a professional: the knowledge of, say, the master of a period replica vessel. It is adequate, though, to understand the terms used, and to be able to make sense of the correlations between recorded conditions, navigational objectives, and operational decisions: sail changes, changes in course, the shifting of ballast and cargo for weight redistribution, storm tactics. The second stage is processing the log: first transcribing, and then attempting to make the correlations above. The log will not provide all the information one could want for doing this; it will not, for example, make completely clear how shifts in the wind correlate with sail changes. It will not provide exact correlations between course steered and wind direction at the same time; exact point of sail at that time will thus remain elusive. My experience with Sultana's logs, however, taught me that these correlations may be guessed at with enough certainty so as to be useful. That in itself was instructive. I was able to construct tables of such correlations for Sultana, and those in turn led to questions about why some decisions were taken in some specific circumstances. The third stage of the process was, then, to discuss these questions with those whose expertise far exceeds my own, and always will: professional mariners, some of whom have spent decades at sea on traditional sailing vessels. These discussions were mentally challenging, but they resulted in a level of understanding of how Sultana behaved at sea, and why her crew worked her as they did, that surpassed anything I could have arrived at on my own. They contributed to interpretations I could present in the book I wrote on Sultana that are more sophisticated than what is usually found in the historical literature, yet written in language accessible to the layperson. We cannot work on these subjects without technical expertise, but our own technical expertise will rarely if ever prove adequate to fully exploit all of what these logbooks can teach us. Collaboration with those who possess the expertise we do not is the only way to do that. Our own expertise does, however, equip us to understand and use what those consulting experts are telling us.

Summary: What Can We Find in an Eighteenth-Century Atlantic Logbook?

As with other eighteenth-century primary source documents, these logbooks have much to tell, and much more to suggest; they were not written for posterity, but for a more immediate purpose. Their most obvious contributions are to the history of navigation, vessel operation, and climatology; but they should not be overlooked by scholars interested in other aspects of the eighteenth-century Atlantic. They contain observations about marine wildlife, geography, harbours and towns, social and cultural attitudes and assumptions, warfare, maritime predation, and commerce. Real life is full of the unexpected, of random happenings, and logbooks are too. Sultana's logs tell of the murder of a Cherokee in Virginia by a white man, as the schooner was charged with transporting the accused for trial. They tell of four wretched “lunatics,” whom they also transported, as there was no place to house them in Williamsburg, Virginia, but the jail. The George/Reward logbook describes the scenery of the West Indies plantations, and offers a basic account of the acquisition and attempted disposition of thirty enslaved people. It recounts the attendance of the author at a musical performance in Kingston, describing the venue as charming and the performance as disappointing. He records a poignant note about the poverty in Cork, Ireland, struck by the throngs of beggars waiting outside the door of every church as services let out. Often, these details offer enough information that the researcher can pursue supplementary sources to fill in what is left out.

Supplementary and Complementary Sources

Nontraditional sources can also prove useful. I have had more success than I expected entering terms from the logbooks into a Google search box and exploring results. For example, I found a description of the entertainment venue in Kingston mentioned in the George/Reward log on the website of a local amateur historian there. Should I choose to, I can now, armed with the name of the place and its brief history, make an archival inquiry much more likely to yield results in a timely manner than I could have without such information.

For commercial voyages, historians interested in maritime commerce can search for the port records recording the entry and clearance of the vessel at its points of origin and destination. These will provide details about the vessel itself, its cargo, and its crew that will likely be missing from the logbook. Not all of these port records survive; archivists in the port or at national repositories should know which ones have, and where they are. I have found that it may require several steps, starting locally, to ascertain that.

For naval logbooks, muster books are invaluable records of personnel matters, even recording the ages and birthplaces of the crew members, as well as their conduct while in service, wages, and expenses. I made an extensive analysis of these for Sultana. Footnote ¹⁸ I would also point out that the United Kingdom Hydrographic Office retains a large collection of the sailing and piloting directions required to be kept by Royal Navy commanders on foreign service, describing the ports of call visited, including what provisions and services were available, what defensive installations were to be found, and what maritime commerce went on there. I used digital images of those kept by Lieutenant Inglis.Footnote ¹⁹

Depending on the researcher's specific interests, references in the logbooks might lead to newspapers, legal records (in the case of the George, vice-admiralty court proceedings), merchants’ correspondence, or other logbooks. For me, Sultana's logbooks, which spanned four-and-a-half years, provided the bulk of the source material I needed for a monograph. The George/Reward logbook, spanning only ten months, will yield a full-length article with a rich narrative, providing enough contextual clues for the location of helpful primary and secondary sources to flesh out the detailed story of an ordinary vessel and her crew navigating the hazards of the British Atlantic.