Land ahoy?

If you’re not able to follow Halley on Twitter, you’ve missed a bit of excitement over the last few days – here’s what happened:

[1 Feb 1700, extract; Lat 52°24′ S] Yesterday in the Afternoon with a fresh Gale at NbW, I steard away ESE, and between 4 and 5 we were fair by three Islands as they then appeard; being all flatt on the Top, and covered with Snow, milk white, with perpendicular Cliffs all round them, they had this appearance, and bearing [*]


The greate hight of them made us conclude them land, but there was no appearance of any tree or green thing on them, but the Cliffs as well as the topps were very white, our people calld A by the Name of Beachy head, which it resembled in form and colour, and the Island B in all respects was very like the land of the Northforeland in Kent, and was as least as high and not less than five Miles in Front, The Cliffs of it were full of Blackish Streaks which seemed like a fleete of Shipps Standing out to us. Wind blowing fresh, and night in hand, and because our vessell is very leewardly, I feard to engage with the Land <or Ice> that night, and haveing Steard in as farr as I durst, I resolved to Stand off and on till day, when weather permitting I would send my boat to see what it was. In the night it proved foggy, and continued so till this day at noon, when by a clear glare of Scarce ¼ of an hour we saw the Island wee calld beachy head very distinctly to be nothing elce but one body of Ice of an incredible hight, whereupon we went about Shipp and Stood to the Northward.

[2 Feb 1700, extract] We Stood to the Norward all day close hald, at night we tackt and Stood to the Southards to spend the dark. [B]etween 11 and 12 this day we were in eminant danger of loosing our Shipp among the Ice, for the fogg was all the morning so thick, that we could not See a furlong about us, when on a Sudden a Mountain of Ice began to appear out of the Fogg…this we made a shift to weather when another appeard more on head with severall peices of loose Ice round about it; this obliged us to Tack, and had we mist Stayes, we had most Certainly been a Shore on it, and we had not beene halfe a quarter of an hour under way when anothr mountain of Ice began to appear…which obliged us to tack again, with the like danger of being on Shore: but the Sea being smooth and the Gale Fresh wee got Clear: God be praised: This danger made my men reflect on the hazzards wee run…and of the inevitable loss of us all, in case we Staved our Shipp which might soe easily happen amongst these mountains of Ice in the Foggs, which are so thick and frequent there.

Gosh, I’m not surprised his crew began to reflect on the dangers of their situation!

We’re witnessing Halley and his crew seeing something – an iceberg – for the first time in their lives and they can’t quite grasp what it is they’re seeing. They initially think it’s land with high chalky cliffs, but then they come to realise it’s nothing but ice. In a later letter, Halley says they couldn’t sound ground at 140 fathoms (≈840ft/256m), but that although he estimates the bergs’ height at around 200 feet [‡] and knows that “not Above an Eight part” of floating ice appears above the surface, he cannot conceive that the ‘islands’ are floating and thinks that they must be grounded.

A tabular iceberg (Photo: Jerzy Strzelecki/Wikimedia Commons)

Now I expect many of you are like me and have rarely experienced total darkness. Last year I spent a few days on the Kent coast (on the North Foreland in fact) and was surprised by how dark it was looking out to sea when almost all the lights were extinguished. I could see only a few metres in front of the hotel (where there was some lighting), but beyond that, nothing but inky blackness.

This gave me some idea of what it must have been like on a seventeenth-century ship in the middle of the ocean, of how nothing would have been visible unless there was moonlight, while daytime visibility would have been little better in a thick fog. It must have been quite terrifying for Halley and his crew when these huge, white ‘mountains’ suddenly loomed out of the fog, dwarfing their little ship. It seems to me they were extremely lucky to escape the icebergs – and it’s a horrid thought that had they hit one, they would all have been lost and no-one would ever have known what happened to them.

Icebergs looming out of the fog (Photo: W. Pfahler/Wikimedia Commons)

But Halley’s one of those people who seems to make his own luck and the Paramore, while not yet out of danger, has made it through the worst and is now heading towards warmer climates.

[*] This is an indicative drawing by me of Halley’s original sketch; it is not identical.

[‡] This number is no longer clear in the letter (TNA, ADM 1/1871) as the edge is frayed, but Thrower gives it as 200. We’ll take a look at the letter on the relevant date.


Instructions for Halley’s second voyage

Halley received his commission to be Master and Commander of Paramore on his second voyage on 23 August 1699, and his instructions for the voyage on the 12 September.

His instructions were almost identical to those he received for his first voyage, namely:

  • to measure the variations of the compass (magnetic variation)
  • to ascertain the latitude and longitude of the places he visits, particularly in the West Indies
  • to discover the unknown lands in the south Atlantic

only this time, the section on the Terra Incognita refers to finding it specifically between the latitudes of 50 and 55 degrees south, which Halley himself asked to be included in his instructions in a letter to the Admiralty.

Here are his instructions in full (remember ye/ym = the/them):

Whereas his Majesty has been pleased to lend his Pink ye Paramour, for your proceeding a second time w:th her on an Expedition to Improve ye knowledge of the Longitude & variation of ye Compass, which ship is now Compleatly mann’d, stored and victualled at his Majesty’s Charge for ye said Expedition, you are therefore hereby required and directed forthwith to proceed with her according to ye following Instructions.

You are without loss of time to Sett Saile with her, and proceed to make a Discovery of ye unknowne South lands between ye Magellan Streights & ye Cape of good hope, between ye Latt:d of 50 & 55 South, if you meete not with ye land sooner observing ye variation of ye Compass with all ye accuracy you can, as also ye True Scituation both in Longitude & Latt:d of ye ports where you arrive.

You are likewise to make ye like observations at as many of ye Islands, in ye Seas between ye aforesaid Coasts, as you can (without too much deviation) bring into your Course.

In your returne home you are to visit ye English West India Plantations, or as many of ym as conveniently you may, & in them to make such observations as may contribute to lay them downe Truly in their Geographicall Scituation, & in all ye Course of your Voyage, you must be carefull to omitt no oppertunity of noting ye variation of ye Compass, of which you are to keep a Register in your Journall.

You are for ye better lengthning out your provisions, to put ye Men under your Comand, when you come out of ye Channell, to six to four Men’s allowance assuring ym that they shall be punctually paid for ye same at ye End of ye Voyage.

You are during ye Terme of this Voyage, to be very carefull in Conforming your selfe to what is directed by ye Generall printed Instructions annexed to your Comission, with regard as well to his Majesty’s honour as to ye Governement of ye ship under your Comand; and when you returne to England, you are to call in at Plymouth, & finding no orders there to ye contrary, to make ye best of your way to ye Downes & remaine there till further order.

Cape Horn is roughly on the same latitude that Halley's headed for (via Wikipedia Commons)

Cape Horn is roughly on the same latitude that Halley’s heading for (via Wikimedia Commons)

Halley’s instructions

I will write about how Halley, an astronomer and mathematician, came to have command of a Royal Navy ship in a future post, but I thought I’d begin by explaining the purpose of his voyage.

Halley was interested in navigation throughout his life, and especially the search for a method of finding longitude at sea and the variation of the magnetic compass (magnetic declination*). Longitude is your position east or west of a reference meridian and it was very difficult to find at sea, with accurate, practical methods only becoming available in the later eighteenth century through the time-keepers of John Harrison and the lunar-distance tables of Nevil Maskelyne. The difficulty of finding longitude applied not just to the position of a ship at sea, but also to the port to which it was heading. As the Astronomer Royal, John Flamsteed, remarked, ‘Tis in Vain to talke of the Use of findeing the Longitude at Sea, except you know the true Longitude and Latitude of the Port for which you are designd’.[1] In other words, knowing the longitude of your ship was of little use, if the place you were sailing towards was inaccurately located on your chart, and so improving the accuracy of maps was another concern of the period.

Halley was also interested in the related problem of compass variation and he published two important papers on the subject in 1683 and 1692. In the first he explained that the ‘deflection of the Magnetical Needle from the true Meridian’ was of great importance in navigation and that the ‘neglect thereof, does little less than render useless one of the noblest Inventions mankind ever yet attained to’, since if a navigator failed to adjust his course for the local variation, he would sail in the wrong direction.[2] Halley was critical of work that had been done on the subject to date, complaining that no-one had yet sought to establish a general rule of the variation, an endeavour that was characteristic of Halley. He therefore sought to provide such a rule in his paper and proposed that both magnetic declination and secular variation** could be explained if the ‘whole Globe of the Earth is one great Magnet, having Four Magnetical poles’.[3]

Halley refined this theory in his 1692 paper by suggesting that the Earth comprised an external shell and an inner nucleus, and that each possessed two magnetic poles and rotated at slightly different speeds, thereby accounting for the observed features of magnetic variation.[4] (He also suggested there might be more than one inner globe and that these might be habitable, but we’ll draw a veil over that one!) Halley called on mariners to ‘use their utmost Diligence to make, or procure to be made, Observations of these Variations in all parts of the World’ in order to advance the study of the declination, and it was perhaps this that gave him the idea of undertaking the task for himself, as it was shortly after the publication of this paper that his voyage was first proposed.

I will discuss that proposal and the events that followed in a later post, but for now we’ll just look at the instructions he received from the Admiralty on 15 October 1698:

Halley’s Instructions (© National Archives (£), ADM 2/25, pp 155-156)

Whereas his Ma[jes]ty. has been pleased to lend his Pink the Paramour for Your proceeding with her on an Expedition, to improve the knowledge of the Longitude and variations of the Compasse, which Shipp is now compleatly Man’d, Stored and Victualled at his Mats. Charge for the said Expedition; You are therefore hereby required and directed, forthwith to proceed with her according to the following Instructions.

You are to make the best of Your way to the Southward of the Equator, and there to observe on the East Coast of South America, and the West Coast of Affrica, the variations of the Compasse, with all the accuracy You can, as also the true Scituation both in Longitude and Latitude of the Ports where You arrive.

You are likewise to make the like observations at as many of the Islands in the Seas, between the aforesaid Coasts as You can (without too much deviation) bring into Your course: and if the Season of the Yeare permit, You are to stand soe farr into the South, till You discover the Coast of the Terra Incognita, supposed to lye between Magelan’s Streights and the Cape of Good hope, which Coast You are carefully to lay downe in its true position.

In Your returne home You are to visit the English West India Plantations, or as many of them as conveniently You may, and in them to make such observations as may contribute to lay them downe truely in their Geographicall Scituation. And in all the Course of Your Voyage, You must be carefull to omit no opportunity of Noteing the variation of the Compasse, of which You are to keep a Register in Your Journall.

You are for the better lengthning out Your Provisions to put the Men under Your Comand when You come out of the Channel, to Six to four Mens Allowance, assureing them that they shall be punctually pay’d for the same at the End of the Voyage.

You are dureing the Term of this Voyage, to be very carefull in conforming Your selfe to what is directed by the Generall Printed Instructions annex’d to Your Comission, with regard as well to his Mats. honor, as to the Government of the Shipp under Your Comand, and when You returne to England, You are to call in at Plymouth and finding no Orders there to the contrary, to make the best of Your way to the Downes, and remaine there till further Order. Giving Us an Accot. of Your arrival.

So Halley had three tasks on his voyage:

  • to measure the variations of the compass, in order to identify a general theory that would be of use to navigators
  • to ascertain the longitude and latitude of the places he visits, in order to improve maps and charts
  • to seek the coast of the Terra Incognita in the southern Atlantic

Was Halley successful in his mission? Well, you can follow the progress of his expedition via his Twitter account @HalleysLog and he’ll tell you himself!

This post was first published on 22 October 2012 and revised on 22 October 2016.

* magnetic declination (or variation) is the angular difference between magnetic and geographic north

** secular variation is the variation of the variation over time


[1] The Correspondence of John Flamsteed, ed. by Forbes, Murdin, and Willmoth, 3 vols (Bristol, 1995), Vol. 2, p. 641.

[2] Halley, ‘A Theory of the Variation of the Magnetical COMPASS’, Philosophical Transactions, vol. 13 (1683), p. 208.

[3] Ibid, pp. 215-6.

[4] Halley, ‘An Account of the cause of the Change of the Variation of the Magnetical Needle’, Philosophical Transactions, vol. 16 (1686-92), pp. 567-8.