The Clock That Changed the World: How John Harrison’s Portable Clock Revolutionized Sea Navigation in the 18th Century

In the ear­ly eigh­teenth cen­tu­ry, a pock­et watch could keep rea­son­ably accu­rate time, give or take a minute per day. This may not sound too bad, giv­en how we now regard even the most advanced tech­nol­o­gy of that era. But it cer­tain­ly was­n’t good enough for marine nav­i­ga­tion: each day, a ship could tol­er­ate its clocks gain­ing or los­ing only a cou­ple of sec­onds. With­out prop­er reli­able infor­ma­tion about the time, sailors on the open sea had no way of know­ing quite where they were. More specif­i­cal­ly, the sun told them how far north or south they were, their lat­i­tude, but they did­n’t know how far east or west they were, their lon­gi­tude.

The­o­ret­i­cal­ly speak­ing, the “lon­gi­tude prob­lem” was eas­i­ly solv­able. You could cal­cu­late it, writes Gear Patrol’s Ed Est­low, “by sight­ing the sun at high noon where you were, and if you had a good enough clock for the time back home, you could com­pare the two and, with some sim­ple math­e­mat­ics, deter­mine your posi­tion.” But engi­neer­ing such a good-enough clock in real­i­ty took about half a cen­tu­ry. “In 1714, the British gov­ern­ment offered the huge prize of £20,000 (rough­ly £2 mil­lion today) to any­one who could solve the lon­gi­tude prob­lem once and for all.” But the mon­ey was­n’t ful­ly claimed until 1773, by a York­shire clock­mak­er John Har­ri­son.

Har­rison’s name looms large in the annals of chronom­e­try, and not with­out rea­son. His work of invent­ing an accu­rate ship clock involved the cre­ation of five dif­fer­ent mod­els, known by his­to­ri­ans as H1 through H5. H1 was a portable ver­sion of the kind of siz­able wood­en clock with which he’d already made his name. It was only in with H4, in 1765, that he real­ized small is beau­ti­ful, or rather accu­rate, at least if equipped with over­sized inter­nal bal­ance wheels to hold up more reli­ably against the con­stant move­ment of a ship at sea. This design worked with­out a hitch, but even so, the Board of Lon­gi­tude only saw fit to award him half the mon­ey offered.

Nei­ther Har­rison’s solv­ing of the lon­gi­tude prob­lem nor his receipt of a dis­ap­point­ing­ly halved prize seem to have stopped his obses­sion with build­ing ever-bet­ter time­keep­ing devices. This comes as no sur­prise giv­en the qual­i­ties of mind that emerge in “The Clock That Changed the World,” the episode of BBC’s A His­to­ry of the World at the top of the post. While work­ing on H5, Har­ri­son “sought the sup­port of King George III” (he of the famous mad­ness). “The King, a nat­ur­al philoso­pher in his own right, test­ed H5 him­self and promised Har­ri­son his sup­port.” That sup­port final­ly got the elder­ly Har­ri­son his promised amount and then some, but one sens­es that — like any pur­suit wor­thy of one’s life­long ded­i­ca­tion — it was nev­er real­ly about the mon­ey.

Relat­ed con­tent:

New Archive Reveals How Sci­en­tists Final­ly Solved the Vex­ing “Lon­gi­tude Prob­lem” Dur­ing the 1700s

How Clocks Changed Human­i­ty For­ev­er, Mak­ing Us Mas­ters and Slaves of Time

The Plan­e­tar­i­um Table Clock: Mag­nif­i­cent 1775 Time­piece Tracks the Pass­ing of Time & the Trav­el of the Plan­ets

How Did Car­tog­ra­phers Cre­ate World Maps before Air­planes and Satel­lites? An Intro­duc­tion

Based in Seoul, Col­in Mar­shall writes and broad­casts on cities, lan­guage, and cul­ture. His projects include the Sub­stack newslet­ter Books on Cities, the book The State­less City: a Walk through 21st-Cen­tu­ry Los Ange­les and the video series The City in Cin­e­ma. Fol­low him on Twit­ter at @colinmarshall, on Face­book, or on Insta­gram.

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