Temporary insanity in tropical waters

Richard de Grijs
Sydney, Australia


Frontispiece to the second edition (1639) of John Woodall’s The Surgion’s Mate, promising to outline “[t]he cures of the Scurvey [sic] … and of the Calenture.” Line engraving by George Glover. Wellcome Collection.

So, by a calenture misled,

The mariner with rapture sees,

On the smooth ocean’s azure bed,

Enamell’d fields and verdant trees:

With eager haste he longs to rove

In that fantastick scene, and thinks

It must be some enchanted grove;

And in he leaps, and down he sinks.1


It was the heat, that relentless, oppressive heat. After weeks of becalmed conditions in the Doldrums, excessive exposure to the sun’s unrelenting heat could render any sailor feverish and delirious—a case of “calenture.” Heatstroke, sunstroke, burning fever, coup de soleil, ictus solis, heat apoplexy, and heat asphyxia have all been called calenture, either individually or collectively.2 A term borrowed from the Spanish calentura (literally, fever or “to be warm”), “it may be inferred that the [British] sea surgeons, in dealing with that in which the Spaniards were more skilled than themselves, adopted with the name the Spanish treatment of the disease.”3

By all my experience … the calenture is no other thing than a contagious fever; for the most part suddenly assaulting seamen, sometimes it is with paroxysms [sudden recurrence], sometimes continues, and hath its fits—hot and cold—in some, and that very violent, even to the loss of senses.4

Those who survived the often fatal urge to jump overboard, to soar, or to fly from the ship’s deck5 reported powerful, irresistible hallucinations. Combined with the paralyzing boredom from inactivity and the incessant ambient heat, sailors—or, indeed, convicts6—from cooler, more temperate climes would picture the vast expanse of the ocean as a cool, green pasture or grassy meadow reminiscent of the pastoral landscape of home,7 not unlike a fata morgana appearing to the weary, dehydrated desert traveler8:

The deep blue of the sea, scarcely wrinkled by the breeze, stretched around, and the waterline was like an azure cincture clasped, where the glory of the sun hung, by a plate of gold; but over the side the water was of an exquisite transparent green, in which you could see the metal hull of the vessel wavering till a bend hid it and it was enough to possess a man, half-blinded with the heat that came off the brassy glare under the sun, with a calenture to look into the grass-like emerald profound, and to think of the coolness and sweetness to be got by a lazy floating in the serene surface of that fathomless depth.9

The natural impulse to take that final step over the ship’s protective railing quickly became overwhelmingly alluring; “one wanted at all risks to take a header and float lazily in the cool, grassy, serene element”10:

About twelve years ago [in 1897] a young man was found climbing over the rail of a vessel sailing in the tropics, preparatory to jumping into the sea. In explanation of his conduct he said that he saw his sister in a green field gathering flowers, and was climbing over the gate to go to her.11

Most reported fatalities describe sailors left to deal with their own mental demons, staring wistfully into the deep, blue profound, creeping forward fathom by fathom.12 They describe being “lured” or “hypnotically attracted” to the sea,13 overcome by lethargy, perhaps reminiscing of life back home.14

And unless they are detained by Force, they leap into the Sea; and this Symptom is the Pothognomonick [characteristic] Sign of this Disease. … Young, lusty Men of a Sanguine Complexion are most obnoxious to it.15

References to calenture as a medical affliction started to appear in diaries and literary works from the late sixteenth century. Its first use dates from 1582, with additional cases reported infrequently16 throughout the 1590s17 and the early seventeenth century:

THE Calenture at the first apprehension afflicts the Pacient with great paine in the head, and heate in the bodie; which is continuall or increasing, and doth not diminish and augment as other Feuers [Fevers] doo: and is an introduction to the Tabardilla, or Pestilence; whereof next is intreated: but then the bodie will seeme very yellow.18

[T]he 16. of May [1604] wee passed the line [the Equator], where many of our men fell sicke of the Scurvy, Calenture, Bloudy flux [dysentery], and the Wormes, being left to the mercie of God, and a smale quantitie of Lyman juyce every morning: our physition shipt for that purpose being as unwilling as ignorant in anything that might helpe them.19

To returne: in changing so many parallels, the weather increast from warme to raging hot, the Sunne flaming all day, insomuch that Calentures begun to vexe us.20

Occasional reports of calenture-induced fatalities continued to surface during the seventeenth to nineteenth centuries. However, writing in 1745, William Smith, Rector of St. John’s in Nevis (West Indies), commented:

Having heard so often of a Calenture, I expected to meet with some instances of it, even before I arrived in the West-Indies; but they are now grown very scarce, for I never saw above one person labouring under it: He was continuously laughing, and if I may be indulged in the term, merrily mad: One day in the height of his frenzy, he jumped overboard in Charles-Town Bay, but was luckily saved from drowning by one of his Sailors, or from being devoured by some ravenous Shark.21

Only a few instances of calenture have been reported since that time. Yet, anecdotal evidence published in 1983 in the British Journal of Medical Psychology suggests that more than half of one ship’s crew had experienced a strong urge to jump overboard.22 More recently, the death of British media magnate Robert Maxwell, in 1991, has been tentatively linked to calenture.23 Even today, the approximately 4% of sailors gone “missing at sea” might have succumbed to that temporary insanity associated with heat exposure.24

Today, at-risk seamen are recommended to stay well away from their ship’s railing, in company, or below deck on hot and calm nights. Historically, however, “[t]hey appl[ied] Cauteries most unmercifully,”25 that is, those susceptible to calenture “were most commonly relieved by plentiful Bleeding.”26 In his discussion of Robert James’ medical dictionary, Burr (1929) describes a case treated by one Dr. Oliver:

A sailor, thirty years old, on a man-of-war [war ship], in the Bay of Biscay, became suddenly violent and needed four men to prevent his jumping overboard. He looked as furious as a lion. He cursed those who held him. He cried out continually he would go to the green fields. There was burning heat all over his body. “There was a disorderly motion of the blood in the artery on taking the pulse but I could distinguish no distinction or vibration of pulse.” Oliver bled him from three places, the arm, the frontal, and the jugular. The blood was thick but finally he got in all 50 oz. The patient became quieter, slept, and awoke well, save for weakness and muscle soreness.27

As early as 1625, the Royal Navy prescribed a treatment adopted from Spanish practice. Aiming to avoid risky interventions, including over-purging, bleeding, and starvation (which could exacerbate a sailor’s poor health and potentially induce scurvy), it consisted of

… alexipharmics [antidotes] and cordials, by brandy and other stimulants, that the animal, vital, and natural parts may be defended from the venomous danger of the disease; and in evacuation, and regimen of diet; all these being as suddenly put in practice as time will serve, the disease being sudden and fierce in itself, repeating the same, then evacuation by a glyster [clyster] or suppository; and after its action a moderate abstraction of blood, low liquid diet, and after two or three days in the name of God give him a dose of laudanum [opium], and you shall find it often to procure health without further help.28

Despite the rarity of reported cases, some of the greatest literary works wholeheartedly embraced calenture in their prose or poetry. Among the earliest adaptations we find Jonathan Swift’s satirical poem about the speculative South Sea Bubble of 1721 and Daniel Defoe’s The Life and Strange Surprizing Adventures of Robinson Crusoe (1719): “Yet even in this voyage I had my misfortunes too; particularly that I was continually sick, being thrown into a violent calenture by the excessive heat of the climate.”29

A century later, Romantic poets like William Gilbert in The Hurricane (1796) and William Wordsworth in The Brothers (1800) and To Enterprise (1820?) found poetry in this strange, maritime disease. And although numerous literary greats embraced the affliction, perhaps the greatest literary contribution is found in Herman Melville’s dramatic masterpiece, Moby Dick (1851):

These are the times, when in his whale-boat the rover softly feels a certain filial, confident, land-like feeling towards the sea; that he regards it as so much flowery earth; and the distant ship revealing only the tops of her masts, seems struggling forward, not through high rolling waves, but through the tall grass of a rolling prairie: as when the western emigrants’ horses only show their erected ears, while their hidden bodies widely wade through the amazing verdure.30


End notes

  1. Swift, J., 1721. Upon the South Sea Project: vi, vii. http://www.online-literature.com/swift/poems-of-swift/43/.
  2. Fayrer, J., 1876. On Sunstroke. The Indian Medical Gazette, 11(10), 277–278.
  3. Woodall, J., 1625. Cited in Smart, W. R. E., 1883. On the so-called epidemics of seamen, more particularly with reference to fevers. Trans. Epidemiol. Soc. London, 2, 68–89. P. 73.
  4. Ibid.
  5. Macleod, A.D., 1983. Calenture – missing at sea? Brit. J. Med. Psychol., 56, 347–350.
  6. Hobart Town Advertiser (Australia), 5 April 1850. Convicts. P. 4. Citing the Daily News, 12 December (1849).
  7. Quincy, J., 1717. Lexicon physico-medicum, or a new physical dictionary, explaining the difficult terms used, with some account of the things signified by such terms, collected from the most eminent authors, and particularly those who have wrote upon mechanical principles. London, Andrew Bell, William Taylor and John Osborn.
  8. Jacobs, F., 2014. 650 – Reverse Calenture: Drowning in the Sahara. Big Think, Strange Maps. https://bigthink.com/strange-maps/650-reverse-calenture-drowning-in-the-sahara/.
  9. A Seafarer, 2 May 1885. The Last Man. Hamilton Spectator (Victoria, Australia). P. 1.
  10. Russell, W.C., 13 June 1885. Tales and Sketches. A Strange Voyage. Chapter XXVII—We Plan a Race. Leader (Melbourne, Australia). P. 33.
  11. Knight, M., 1909. Letters, Notes, Etc.: A Case of Calenture. Brit. Med. J., 1(2525), 1276.
  12. Russell, 1885. Op. cit.
  13. Macleod, 1983. Op. cit.: 348.
  14. Union of International Associations, 2020. Calenture. The Encyclopedia of World Problems & Human Potential. http://encyclopedia.uia.org/en/problem/134303.
  15. The Bega Gazette and Eden District or Southern Coast Advertiser (New South Wales, Australia), 14 July 1883. The Doctor’s House. P. 1.
  16. Society for the Diffusion of Useful Knowledge, 1835. Entries in the Old Bills of Mortality. The Companion to the Almanac; or Year-Book of General Information. P. 29; Burr, C. W., 1929. Dr. James and his Medical Dictionary. Annals of Medical History, 1(2), 180–190.
  17. Nashe, T., 1593. Christs Teares over Jerusalem. London, James Robert. F. 45; Nashe, T., 1596. Have With You To Saffron–Walden, Or, Gabriell Harveys hunt is up. London, John Danter. F. 3v; Donne, J., 1597. The Calme. Version published in 1633: https://rpo.library.utoronto.ca/content/calm; Whetstone (Wateson?), G., 1598. The Cures of the Diseased in remote Regions: Preventing Mortalitie, incident in Forraine Attempts of the English Nation. London, Felix Kingston.
  18. Whetstone, 1598. Op. cit.
  19. Middleton, H., 1606. The Last East-Indian Voyage. Containing mvch varietie of the State of the seuerall kingdomes where they haue traded: with the Letters of three seuerall Kings to the Kings Maiestie of England, begun by one of the Voyage: since continued out of the faithfull obseruations of them that are come home. London, T. P.
  20. Herbert, T., Some yeares travels into divers parts of Asia and Afrique …, I. London, Richard Bishop.
  21. Smith, W., 1745. A Natural History of Nevis, and the Rest of the English Leeward Charibee Islands in America. Cambridge, J. Bentham. P. 188.
  22. Macleod, 1983. Op. cit.
  23. Pacific Islands Monthly, April 1992. Lure of the sea proves irresistible. P. 78.
  24. Ibid.; Burr, 1929. Op. cit.
  25. Fryer, J., 1672–1681. A New Account of East-India and Persia, in Eight Letters. London, Richard Roberts. P. 159.
  26. The Bega Gazette, 1883. Op. cit.
  27. Burr, 1929. Op. cit.
  28. Smart, 1883. Op. cit.: 73.
  29. Defoe, D., 1719. The Life and Strange Surprizing Adventures of Robinson Crusoe. London, William Taylor.
  30. Melville, H., 1851. The Gilder. Moby Dick. New York, Harper & Brothers.



RICHARD DE GRIJS, PhD, is a professor of astrophysics at Macquarie University in Sydney, Australia. He has a keen interest in the history of science and navigation. Richard is also a volunteer guide on the historical tall ships at the Australian National Maritime Museum, where he additionally consults on matters related to the “longitude problem.”


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