‘Knots an hour’

 (by Commander Alastair Wilson, R.N.)

Since the 1890s or thereabouts, it has been drummed into the young seaman that a knot is a unit of speed, namely, one nautical mile per hour; and that consequently only the uneducated speak of “knots per hour” or “knots an hour”. It was therefore inevitable that Kipling’s frequent use of this expression should grieve a number of seafaring readers, as the pages of the Kipling Journal testify.

In 1953 and 1954, however, the Mariner’s Mirror, the quarterly journal of the Society for Nautical Research, contained several letters from members of that Society who produced a number of 20th century instances of “knots an hour” being used by men eminent in nautical literature, the Merchant Navy and the Royal Navy. Further inquiry has persuaded us that this practice was even more widespread and longer-lived than the Mariner’s Mirror indicated. We do not maintain that “knots an hour” was ever logical or correct: what we do say is that Kipling erred in such extremely good company that it is grossly unfair to blame him.

To explain this opinion, we must get down to first principles.

Distances at sea are measured in terms of the nautical mile, which is defined as being one minute of latitude on the earth’s surface at 48º latitude, this detail being needed because the earth is not perfectly spherical, but is an oblate spheroid, slightly flattened at the poles. A nautical mile is 6,080 feet, about one seventh longer than the land, or statute mile. (With splendid illogicality, modern charts mark depths in metres, but the nautical mile, which has no convenient exact relationship to the kilometre – 1 n.m. = 1.9141 km. – is still the basic unit of length, because of its relationship to a degree of latitude.)

The “knot” reflects the fact that the log-line of the “common log”, “hand log” or “log-ship” used by seamen from time out of mind to measure their vessel’s speed was marked at appropriate intervals by knots, literally.

An excellent description of the process is given in A Roving Commission, the reminiscences (1897) of Commander Crawford Pasco, Royal Navy:

At sea, the senior midshipman of the watch had to “heave the log” every hour to ascertain the ship’s speed (primarily to establish the ship’s position by ‘dead reckoning’).

A mizzen-topman, i.e. a responsible man from the sailors who worked in the after part of the ship] had to hold the reel, at the end of which was the log-ship, a flat piece of wood in the form of a quadrant, with a radius of six to eight inches, the base of which (the arc of the circle) was loaded with lead to keep it in the water while the upper corner floated. The two lower corners had each a hole, presenting a firm resistance to maintain its place when once thrown into the water. A few fathoms of line called ‘stray line’, to allow the log-ship to perform its duty (i.e. to let it out of the eddy wake following the ship) was marked with a piece of bunting to commence the marking of knots which represent nautical miles. Between the stray line mark and the first mark was eight fathoms (48 feet), each knot being marked with a small strand through the line, with one knot in the first, two knots in the second, and so on to six, and between each knot was a half-knot [i.e. half-way between each marker, at 24 feet intervals, a knot was formed in the log-line itself.]

The quartermaster held the sand-glass ready as the stray mark went over the lee quarter, and the midshipman called out “Turn”. The log-glass was turned, and the instant the sand ran out the quartermaster called “Stop”, and the line was kept from running out further.

The mid reported to the lieutenant of the watch, “She is going five-and-a-half, sir”, or whatever it might be.

That officer, if judicious and painstaking in his duty, had watched through the hour the fluctuations of the ship’s progress by an increase or decrease in the wind, or other circumstances affecting her speed, and would reply to the mid who had to mark the log-slate, “Give her seven”, or it may be only four.

Above, I have said that the distance apart of the knot markers was eight fathoms, but I have not mentioned the length of the sand-glass. The long glass was twenty-eight seconds but there is a short glass of half that time, fourteen seconds, for this reason that twenty-eight seconds bears (very nearly) the same proportion to an hour as eight fathoms does to a nautical mile. [The exact time ought to be 28.42 seconds.] But when a ship’s speed exceeds five or six knots it would carry out such a length of line that, by using the short glass, the half knots equalled knots, so that four-and-a-half became nine.

The first description of a log-ship and a line, I have heard, occurs in Bourne’s Regiment of the Sea, 1573”.

Since the distance between knots was only eight fathoms, 48 feet, and the time a matter of 28 (or 14) seconds, the terms “knots an hour” would seem to be anomalous.

Nevertheless, according to The Art of Navigation in Elizabethan and Early Stuart Times by Lieutenant Commander D.W. Waters, Royal Navy (1958), “knot” was used to mean a nautical mile [the distance, purely and simply] as early as 1625. There is ample evidence that it became common and remained common throughout most of the nineteenth century, and lingered on into the twentieth amongst those whose early nautical training took place before the nineties.

To give some selected examples, “knots an hour” occurs in:

  • Captain Marryat’s well-known stories of the 1830s and `40s
  • Journals kept by Captain Sir William Dillon, Royal Navy, at about the same period. Sometimes when he had originally written “knots”, he later inserted “an hour”
  • An official report on trials carried out by H.M. Paddle Despatch Vessel Helicon in 1865
  • Publications by two Directors of Naval Construction
  • Many official and semi-official text books issued up to and after 1900
  • Books by Joseph Conrad and John Masefield, who were seamen before they took to literature
  • The instructions issued by the Board of Admiralty to the flag officers taking part in the manoeuvres of 1897, described by Kipling in A Fleet in Being
  • The memoirs and writings of many senior naval officers, including Admiral of the Fleet Lord Jellicoe’s The Grand Fleet (1919)
  • The speech by the First Lord of the Admiralty introducing the Naval Estimates of 1907-08

In the face of this evidence it would be difficult to argue that the error if such it is, had not gained a pretty firm foothold, and we find it surprising that there seems to have been no record of the crusade which must have been needed to eradicate it. We can suggest a tentative date for the “reformation” in American usage, since it is said that the 1881edition of Bowditch’s American Practical Navigator, a standard textbook mentioned by Kipling in Captains Courageous (page 124), amended “knots an hour” to “knots” throughout its pages.

In England, all we seem able to say at the moment is that naval cadets in HMS Britannia about 1892-93 were taught that “knots an hour” should be avoided, although, as we have seen, it continued to be used by some older officers and officials to the end of their lives.

Kipling appears to have picked the term up from the older school and continued to use it in their excellent company until quite a late date, after which “knots” was substituted for “knots an hour” in the Sussex and Burwash editions of his works. We do not think he can fairly be blamed.


©Alastair Wilson and P W Brock 2006 All rights reserved