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The ArchivesThemesCharts, Maps and Route Knowledge

Charts, Maps and Route Knowledge

This theme covers the wind systems, seasonal calendars, charts, pilot books and hired pilotage by which a shipmaster knew which way round the ocean he had to go and in what month.

Also writtenRoute knowledge; Sea roads; Rutters and waggoners; Pilot books and sailing directions

Wind and calendar decided which water a ship could use, and in which months; charts and pilot books recorded the coasts those winds delivered a ship to. What pirates took of either leaves almost no trace.

What route knowledge was

Four things travelled under the name. The standing wind system of trades, calms and westerlies. The seasonal calendar, which mattered most in the Indian Ocean, because the monsoon reverses. The chart and the pilot book, the written deposit of the first two plus what neither of those contains: soundings, bars, anchorages, the look of a headland. And local pilotage, unwritten and for sale. Together they constrain a voyage in that order: month, then track, then book, then pilot within soundings. Position finding and the reckoning are at navigation and seamanship.

The winds

The prevailing winds could trap a company. Johnson's General History has Bartholomew Roberts's men, unable to fetch Brava, driven back "with the Trade-Wind, for the West-Indies", 700 leagues to Surinam on one hogshead of water.1

The season at the gate

A New Directory for the East-Indies states the mechanism. Its six-month rule: a monsoon sets in about six months after the opposite one sets in at that place. The south-west monsoon reaches Surat by mid-April but is not well set in from Bombay to Cochin until late May or mid-June, so it is a moving front rather than a single date. On the Arabian coast it gives south-westerlies from early April to the end of August, reversing to easterlies in September, and advises that ships leaving Mocha eastward from the end of August onward should keep southerly for the west-south-west winds that blow only till the middle of September, remarking that many ships have lost their passage for want of that attention. The edition is of 1791, sixty-six years after the period, though the wind regime it describes is a physical constant.2

Set that against September 1695. The Fateh Muhammed was taken in the Bab al-Mandab passage in late August or early September, the Ganj-i-Sawai on passage from Mocha to Surat, the day being disputed, while the indictment of 1696 dates an attack on "a Moorish Ship" forty leagues from Surat to 28 September, a charge that answers better to the Fateh Muhammed than to the Ganj-i-Sawai. A squadron off the strait that week lay there as the eastbound passage out of the Red Sea closed. No pirate is recorded giving a seasonal reason for a station, and none of it is attributed to Henry Every. The outcome is plain enough: pirates were repeatedly at that strait in that season.3

What could be taken out of a prize

At the Cape Coast trial Edward Crisp, Captain Trengrove and Captain Sharp acknowledged that the good usage they met with was chiefly through Harry Glasby's means, "who often interposed, for leaving sufficient Stores and Instruments on Board the Ships they had robbed". Stripping a prize was routine enough that leaving some was worth pleading at a capital trial.4

The word is "Instruments", unqualified, and the same print says "Surgeon's capital Instruments" elsewhere, so these were probably, though not certainly, the navigational kind.

William Snelgrave was taken on the Guinea coast in 1719. Asked how his ship sailed both large and on a wind, he answered truly, regretted it, and reflected that his journal "would have made it plainly appear". In his great cabin the crew broke up the writing cabinets and emptied two chests of books over the side as "Jaw-work enough ... to serve a Nation". Those were law books.5

Dividers of 4.2 inches have come off the wreck identified as Queen Anne's Revenge, with a brass sector for working proportions, and are reported to be nearly identical to a pair from the Whydah Galley. Dividers are chart-work tools. Where the knowledge could not be lifted from a book it was taken with the man who held it: see forced men.6

The gap where the charts should be

No source yet found records a named company taking a named chart, atlas or pilot book out of a named prize. The word "chart" does not occur in a navigational sense anywhere in Johnson's General History, where "draught" is used of a ship's depth of water, the shape of a bay and a legal instrument, and Snelgrave mentions none.7

Three readings of that silence stay open: that charts were too ordinary to record; that these sources are uninterested in navigation; or that companies took the man rather than the book. Survival bias sharpens the silence: a chart in use was folded, soaked and thrown away, and the charts that survive in libraries are characteristically the ones that were not used. No golden-age treasure map is known; the map with a cross on it is a later fiction.

The hole here is documentary. The record proves that stores and instruments were stripped from prizes, that a captured journal was read for intelligence, and that chart-work tools have come off a wreck identified as a pirate ship. It cannot show a company owning a pilot book, or taking a named chart from a named ship. The monsoon mechanics rest on a directory of 1791, no period sailing directions for those waters having been found. A search of Admiralty examinations for chart, draught, waggoner and platt would show whether such things were itemised. The Brava passage and its figures come from the 1724 narrative alone; the identification of the wreck is the excavators' argued conclusion, and the Whydah dividers are known only through their comparison with the pair from that site.

What the evidence does not settle

Pirates and pilot books

  • Whether any pirate company took or used a pilot bookUnverified

Monsoon timing

  • Monsoon and Red Sea timing rest on an 1791 directoryUnverified

Wreck navigation instruments

  • Whether the Queen Annes Revenge dividers were plunder is unresolvedUnverified

Each line is one question with its own grade, taken from the register where a claim carries it. Nothing here is graded as a whole.

Sources for this record

Every statement above that rests on a checked claim carries a small number; the numbers lead here. Each entry gives what is claimed, how far the record supports it, and where it comes from.

  1. The prevailing winds could trap a company, as when Bartholomew Roberts's men failed to fetch Brava and were driven back with the trade wind to the West Indies, given as 700 leagues to Surinam on one hogshead of water. Unverified Reported, not yet checked against the record. Period narrative: A General History of the Pyrates, 2nd edn 1724, for the Brava episode; A General History of the Robberies and Murders of the Most Notorious Pyrates
  2. An East India sailing directory of 1791, used only for a wind regime that is a physical constant, sets out the seasonal grammar of these waters: a monsoon sets in about six months after the opposite one sets in at the same place; the south-west monsoon reaches Surat by the middle of April but is not well set in from Bombay to Cochin until between the end of May and the middle of June, so that it is a moving front rather than a single date; on the coasts of Arabia and Persia south-westerly winds run from early April to the end of August and reverse to fresh easterlies in September; and ships leaving Mocha to the eastward at the end of August or later should keep southerly for the west-south-west winds that blow only till the middle of September. Unverified Reported, not yet checked against the record. Printed sailing directory: William Herbert, with William Nichelson and Samuel Dunn, A New Directory for the East-Indies, 1791 edition, chapters on the trade winds and monsoons, on the coasts of Arabia and Persia and on Mocha road
  3. The Fateh Muhammed was taken in the approaches to the Bab al-Mandab in late August or early September 1695 and the Ganj-i-Sawai on her passage from Mocha to Surat, the day being disputed, while the 1696 indictment dates an attack on "a Moorish Ship" forty leagues from Surat to 28 September 1695, a charge the research reads as the Fateh Muhammed rather than the Ganj-i-Sawai; that a pirate squadron lay off the strait in exactly the weeks when eastbound Red Sea shipping had to make its passage or lose it is an inference drawn from a directory of 1791 applied backwards, and no source records any pirate stating a seasonal reason for a station. Possible Consistent with the evidence, not established. Printed sailing directory: A New Directory for the East-Indies, 1791; the site's Mughal administration record for the 1695 chronology and its disputed day
  4. Evidence at the Cape Coast Castle trial of 1722 records Edward Crisp, Captain Trengrove and Captain Sharp acknowledging that the good usage they had met with was chiefly through Harry Glasby's means, who often interposed for leaving sufficient Stores and Instruments on Board the Ships they had robbed, alledging, they were superfluous and unnecessary there, which establishes that stores and instruments were routinely stripped from prizes. Unverified Reported, not yet checked against the record. Trial evidence printed in a period narrative: A General History of the Pyrates, 2nd edn 1724, the Cape Coast Castle trial matter
  5. William Snelgrave, taken on the Guinea coast in 1719, records that he was questioned about how his ship sailed both large and on a wind and reflected that his journal, when they looked into it, would have made it plainly appear, which establishes that a captured master's written record was read for operational intelligence; his account of his great cabin records broken writing cabinets and two chests of law books emptied over the side as Jaw-work enough to serve a Nation, and mentions no chart, pilot book or navigational instrument anywhere in the narrative. Unverified Reported, not yet checked against the record. Period narrative, eyewitness of capture by pirates: William Snelgrave, A New Account of Some Parts of Guinea, and the Slave-Trade, 1734, optical text of the Internet Archive copy, long s normalised
  6. The project excavating the wreck identified as Queen Anne's Revenge publishes a pair of dividers of 4.2 inches, described as one of the essential tools used by navigators for determining positions on charts and as nearly identical to a pair recovered from the Whydah Galley, together with a brass sector of 5.1 inches closed and 9.4 inches open for solving problems of proportion; the identification of the site is the excavators' argued conclusion, and the Whydah pair is known only through that comparison. Unverified Reported, not yet checked against the record. Modern archaeology: Queen Anne's Revenge Shipwreck Project, North Carolina Office of State Archaeology, artefact pages for Dividers and Sector; the site identification as reported in the site's modern archaeological reports record
  7. No source yet found records a named golden-age pirate company taking a named chart, atlas or pilot book out of a named prize on a named date, and the word chart does not occur in a navigational sense anywhere in the 1724 General History. Unverified Reported, not yet checked against the record. Period narratives, stated as an absence in the texts examined: A General History of the Pyrates, 2nd edn 1724, full text searched; William Snelgrave, A New Account of Some Parts of Guinea, 1734, full text searched