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Navigation and Seamanship

The knowledge, instruments, arithmetic and bodily skill by which a vessel of 1690 to 1725 was made to know roughly where she was, brought over a bar and worked in a chase, and the consequence that pirate companies, unable to supply that skill, took the men who held it.

Also writtenDead reckoning; The reckoning; Pilotage; The artist; Position finding at sea

Navigation and seamanship covers position finding, the daily reckoning, pilotage within soundings, and the offices in which the skill sat. Winds, seasons and the charts themselves are at charts, maps and route knowledge.

What the practice was

Four things travelled under one name: finding a position out of sight of land; pilotage within soundings, which was local memory held by particular men; the working of the hull; and the office itself, held by the master, his mates and a hired pilot. The period's word for such a professional was artist.

One dimension certain, one deduced

Latitude could be measured: the sun's altitude at the meridian, less the day's declination from a printed table. John Seller's Practical Navigation, the standard English manual, in print from 1669 to 1739, carries the tables and calls the back observation instrument simply the quadrant, telling the reader to "turn your back towards the Sun". Longitude could not be measured at all: it was deduced from the course steered and the distance run, and decayed with every hour. The shape of the age's ocean navigation follows from that asymmetry.1

The log board, and the guess inside it

A log board of six columns took the hours, the knots run "in the space of half a minute", the course and the wind, the log "being commonly hove every two hours"; at noon the master worked the last day up into one course and distance made good. Seller prescribes fifty feet between knots with a half minute glass, on a sea mile of 6000 feet. One quantity was never measured. Leeway "is left to the discretion of the Calculator, to be allowed according to the mould of the Ship", which is to say that the east and west position rested on a guess entered every two hours for weeks.2

The Act for discovering the longitude

The Act for discovering the longitude at sea concedes that "nothing is so much wanted and desired at Sea". It offered up to twenty thousand pounds, half of it held back until a ship appointed by the Commissioners had sailed from Britain to the West Indies without losing her longitude, the run the Atlantic companies were sitting on.3

Latitude sailing

Because one dimension only was certain, outbound ships ran into the latitude of their destination and sailed down it, which made their tracks predictable. That pirates exploited this is Johnson's argument, offered in the 1724 General History as naval policy: they "know what Latitude to lie in, in order to intercept Ships", since "the Latitude is the only Certainty in those Voyages". Whether any named company ever worked the latitudes that way is another question.4

The bar, the lead and the pilot

Inshore the method changed: the lead and line, the bottom brought up on the tallow, and a man who had been there before. At Old Calabar, where Roberts's ships cleaned in 1721, Johnson has a bar with "not above 15 Foot Water upon it, and the Channel intricate", the depth and "the want of a Pilot" being "a sufficient Security to the Rovers"; the company kept its own pilot there, "extreamly well paid". At New Providence, at either entrance "there is a Bar, over which no Ship of 500 Tun can pass". The suppression campaigns that worked were fought largely in hired sloops: see naval suppression.5

William Atkinson, taken off the bar of Cape Hatteras on 3 June 1726, was the one prisoner William Fly's company kept, to pilot them on the New England coast on pain of having his brains blown out. Ordered into Martha's Vineyard he missed it on purpose. On 23 June he advised sending a prize away with six of the pirates in her, leaving four aboard, then directed the seizure. He was acquitted at Boston on 4 July.6

The artist

In the Cape Coast Castle sessions of 1722, printed in the same 1724 volume, the court held that "Artists had the best Pretension to the Plea of Force, from the Necessity Pyrates are sometimes under of engaging such", and acquitted Roberts's master Harry Glasby, who had twice attempted escape and had interposed to leave stores and instruments aboard the ships they robbed. Johnson's volume gives the custom the ruling reasons from: when the pirates met "any good Artist" who would not enter, "it was their Custom to keep him by Force". The plea was allowed in principle and refused where a man had had chances to leave: see forced men, the plea of force and crew voting.7

The chase and the careen

Careening left a ship disarmed and immobile, as Johnson's George Lowther was at Blanco, "just careen'd, with her Guns out, and Sails unbent"; the operation is at careening and havens. A chase turned on a clean bottom, the weather gage and deceit. Three naval officers deposed that HMS Swallow, drawing the Ranger out at Cape Lopez on 5 February 1722, "kept away before the Wind, as though afraid", "making, at the same Time, very bad Steerage".

No navigational record kept by any golden-age pirate company is known: no log board, no reckoning, no traverse table. Such records existed, since the ships were navigated, but nothing can be said of how they were kept. Deliberate interception by lying in a destination's latitude rests on that single passage of the 1724 book, and no named company is established as having practised it. The Cape Coast evidence above is known only as reprinted in the 1724 volume, and until the Admiralty file is read against it, it is not independent of that book's narrative.

What the evidence does not settle

Pirate navigational records

  • Whether any pirate company's own navigational record survives

Cape Coast Castle artist doctrine

  • The artist doctrine is known only from the 1724 reprintUnverified

Pegged traverse board use

  • Whether the pegged traverse board was in general use is unresolved

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. Between 1690 and 1725 latitude could be observed at sea by measuring the meridian altitude of the sun or a star and applying a printed table of declination, while longitude could not be observed at all and was deduced from the course steered and the distance run, degrading with every hour out of sight of land. Unverified Reported, not yet checked against the record. Period printed navigation manual: John Seller, Practical Navigation; or, An Introduction to the whole Art, edition of 1680
  2. The standard English manual of the period sets the reckoning down as a shipboard routine: a log board of six columns recording the hours, the knots, half knots and fathoms run in the space of half a minute, the course steered and the point on which the wind lay, the log being commonly hove every two hours and the last twenty-four hours worked up at noon into one course and distance made good, with fifty feet between knot and knot on the log line, a half minute glass and a sea mile of 6000 English feet, and with leeway not measured at all but left to the discretion of the Calculator, to be allowed according to the mould of the Ship, and the Sail she bears. Unverified Reported, not yet checked against the record. Period printed navigation manual: John Seller, Practical Navigation, edition of 1680, the log board, the daily working up and the section Of the Log-Line and half minute Glass
  3. The Longitude Act, entitled An Act for Providing a Publick Reward for such Person or Persons as shall Discover the Longitude at Sea, offered rewards rising to twenty thousand pounds, half of any reward falling due only when a ship appointed by the Commissioners had sailed from Great Britain to a port in the West Indies without losing her longitude. Unverified Reported, not yet checked against the record. Statute text: The Statutes at Large, vol. 13: 12 Anne to 5 George I, 12 Anne stat. 2 c.15, An Act for providing a publick reward for discovering longitude at sea
  4. The introduction to the 1724 General History of the Pyrates argues that outbound ships ran into the latitude of their destination and then sailed down it, because the Latitude is the only Certainty in those Voyages, and that pirates therefore knew what Latitude to lie in, in order to intercept Ships; that any named company practised deliberate latitude interception rests on that passage alone and is not established beyond it. Unverified Reported, not yet checked against the record. Period narrative: A General History of the Pyrates, second edition, London 1724, the introduction; A General History of the Robberies and Murders of the Most Notorious Pyrates
  5. Johnson's General History states that the bar at Old Calabar carried not above 15 Foot Water with an intricate channel, so that the depth as well as the want of a Pilot was a sufficient Security to the Rovers against men of war, that the pirates kept a pilot of their own for the place who was extreamly well paid according to the Journal of their own Accounts, and that the harbour of New Providence had a bar at either entrance over which no ship of 500 tuns could pass; as a description of pirate practice this rests on that single printed source. Unverified Reported, not yet checked against the record. Period narrative: A General History of the Pyrates, second edition, London 1724, the Old Calabar and New Providence passages; A General History of the Robberies and Murders of the Most Notorious Pyrates
  6. William Atkinson, taken off the bar of Cape Hatteras on 3 June 1726, was the one prisoner William Fly's company detained, to pilot them on the coast of New England on pain of having his brains blown out; he deliberately missed Martha's Vineyard, advised on 23 June that a prize be sent away with six of the pirates aboard so that only four remained, then directed the seizure of the vessel, and was tried at Boston on 4 July 1726 and acquitted. Very likely Strong evidence, short of proof. Trial pamphlet: The printed Boston trial record of the William Fly company, 1726
  7. The Admiralty court sitting at Cape Coast Castle in 1722, in the trial matter printed in the 1724 General History, held that Artists had the best Pretension to the Plea of Force, from the Necessity Pyrates are sometimes under of engaging such, and acquitted Bartholomew Roberts's master Harry Glasby, whose twice attempted escape and whose interposing for leaving sufficient Stores and Instruments on Board the Ships they had robbed were in evidence before it. Unverified Reported, not yet checked against the record. Trial evidence printed in a period narrative: A General History of the Pyrates, second edition, London 1724, the Cape Coast Castle trial matter