Show me the way to go home

Never mind sat­nav, it was the com­pass that rev­o­lu­tionised the way we travel. Jonathan Self nav­i­gates its story, from an­cient China to the Sec­ond World War

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Never mind sat­nav, it was the com­pass that rev­o­lu­tionised the way we travel. Jonathan Self nav­i­gates its story, from an­cient China to the Sec­ond World War

NAUGHTY ele­phants,’ my grand­fa­ther would say, in a tone of ut­ter de­spair, as he strug­gled to teach me the dif­fer­ent points of the com­pass, ‘squirt water. Do you get it now? N is for “naughty” and “north” and is here at the top. E is for “ele­phants” and “east” and is here on the right.’ There were cer­tain core skills that he be­lieved ev­ery child should mas­ter and read­ing a com­pass was one of them. Pos­si­bly, if he’d waited un­til I was five or six and was able to spell, he might have found the go­ing a bit eas­ier. Nev­er­the­less, long be­fore I went to prep school, I was a dab hand at nav­i­ga­tion.

There are, of course, lots of dif­fer­ent nav­i­ga­tion meth­ods. Mariners used to fol­low cur­rents, winds and even fish. Vik­ing sailors re­leased birds in the be­lief that, if they didn’t re­turn to the ship, there must be land nearby. Plants and trees have long guided trav­ellers, as have the sun and the stars. My late mother found her way around Lon­don by way of shops and ho­tels—which led to some strangely cir­cuitous routes, such as Ox­ford Cir­cus to Bond Street Un­der­ground sta­tion via Lib­erty, Fen­wick, Asprey, the Ritz, H. R. Owen, the Con­naught and Clar­idge’s. For the past 1,000 years or so, how­ever, mankind has re­lied al­most com­pletely on the mag­netic com­pass.

The first writ­ten ref­er­ence to lode­stone—a dull, grey rock that has the power to at­tract and mag­ne­tise iron and, if a sliver is sus­pended by a thread, will align it­self north and south—is to be found in the 6th-cen­tury writ­ings of the Greek philoso­pher Thales of Mile­tus.

How­ever, it seems likely that the Chi­nese were the first to un­der­stand its po­ten­tial. There are nu­mer­ous men­tions of it in Chi­nese lit­er­a­ture from the 4th cen­tury on­wards, when lode­stone was em­ployed for the pur­poses of div­ina­tion. In the first cen­tury for ex­am­ple, the Em­peror Wang Mang pos­sessed a prim­i­tive lode­stone com­pass to en­sure he could sit fac­ing south, the im­pe­rial di­rec­tion.

It’s un­clear at what point the Chi­nese used such com­passes for nav­i­ga­tion, but the first de­fin­i­tive de­scrip­tion of a di­rec­tional com­pass—‘a mag­netic nee­dle float­ing in a bowl of water’— is in a book dated 1044.

Proof of the com­pass’s use in the West doesn’t ap­pear un­til 1187, when an English Au­gus­tinian monk called Alexander Neckam wrote that when sailors ‘are ig­no­rant to what point of the com­pass their ship’s course is di­rected, they touch the mag­net with a nee­dle. This then whirls around in a cir­cle un­til, when its mo­tion ceases, its point looks di­rectly to the north’.

Dur­ing the lat­ter half of the 13th cen­tury, some de­sign mod­i­fi­ca­tions—in­clud­ing the ad­di­tion of a ‘wind rose’, which made it pos­si­ble to mea­sure other direc­tions in units or de­grees, a gim­bal to al­low for the mo­tion of the ship and a wooden box to pro­tect the whole de­vice—made the use of mag­netic com­passes prac­ti­ca­ble at sea.

In the space of a very short time, the mer­chant ships of Venice, Genoa, Pisa and Amalfi dou­bled the num­ber of voy­ages they were able to make ev­ery year to the east­ern Mediter­ranean, as nav­i­ga­tion was now pos­si­ble dur­ing the win­ter months. In­deed, it would not be over­stat­ing it to say that the in­ven­tion of the mar­itime com­pass had a very marked ef­fect on in­ter­na­tional trade, as well as mak­ing it fea­si­ble for the Euro­pean na­tions to start ex­plor­ing and colonis­ing dis­tant parts of the world. Christo­pher Colum­bus, Hernán Cortés, Vasco da Gama, our own Sir Fran­cis Drake and oth­ers of that ilk would never have got any­where—or come back—with­out their trusty com­passes.

Ac­tu­ally, I say trusty com­passes, but, for nine cen­turies, they were any­thing but. The sim­ple tech­nol­ogy had sev­eral flaws. To be­gin with, even at their best, com­passes point to mag­netic north rather than geo­graphic north. That they work at all is due to the molten iron in the Earth’s core, which has the ef­fect of turn­ing the whole planet into a gi­ant mag­net.

Like all mag­nets, Earth has two poles, one that at­tracts and one that re­pels. Th­ese poles aren’t aligned per­fectly with true north or south and, to make it more con­fus­ing, they shift from place to place and over time, ac­cord­ing to the move­ments of the magma. Mag­netic vari­a­tion at Lon­don in 1580, for ex­am­ple, was 11.15˚ east, but, by 1850, it had

I say trusty com­passes, but, for nine cen­turies, they were any­thing but

changed to 22.24˚ west. In 1950, it was mea­sured at 9.07˚ west and it is still de­creas­ing at the mo­ment.

By the mid­dle of the 15th cen­tury, nav­i­ga­tors had iden­ti­fied the wan­der­ing pole, although it took sev­eral cen­turies to un­der­stand its cause. Var­i­ous meth­ods were tested to cor­rect the de­vi­a­tion—or, to use the tech­ni­cal word, dec­li­na­tion—of which charts and ta­bles, cre­ated on the ba­sis of pre­vi­ous ob­ser­va­tion, were the most ac­cu­rate. Nev­er­the­less, on long jour­neys, even a small de­vi­a­tion could send one hun­dreds of miles out of one’s way.

An­other is­sue was the qual­ity of the com­pass it­self. After the Scilly naval dis­as­ter in 1707, when four Bri­tish ships con­tain­ing 2,000 men were lost as a re­sult of a mis­take in the fleet’s dead reck­on­ing—which the Span­ish call, some­what mor­dantly, nave­gación de fan­tasía— an in­spec­tion of the fleet’s com­passes was made. Of 506 in­stru­ments ex­am­ined, only 73 could be said to be in any­thing close to work­ing or­der.

Then there was the mat­ter of in­ter­fer­ence. The in­tro­duc­tion of greater quan­ti­ties of iron in ship­build­ing, be­gin­ning with iron nails and end­ing up with iron hulls, played havoc with the re­li­a­bil­ity of marine com­passes.

Over the cen­turies, there has been a great deal of com­pe­ti­tion be­tween dif­fer­ent ex­perts and man­u­fac­tur­ers, with end­less and gen­er­ally un­war­ranted claims as to the re­li­a­bil­ity of one new com­pass over an­other. This isn’t so sur­pris­ing when one con­sid­ers that there were huge so­cial and fi­nan­cial re­wards for those who solved, or at least ap­peared to have solved, the var­i­ous prob­lems. In re­al­ity, it wasn’t un­til the end of the 19th cen­tury, when a more or less de­pend­able ver­sion— the gy­ro­com­pass—was per­fected, that trav­ellers could rely on a sin­gle, com­pletely trust­wor­thy in­stru­ment.

I still have the piece that my grand­fa­ther utilised to teach me the rudi­ments of nav­i­ga­tion, his First World War of­fi­cer’s march­ing com­pass, for which he can have had very lit­tle use at the time, as he spent most of the war in charge of Wool­wich Arse­nal (the ac­tual arse­nal, not the foot­ball team). It has ac­com­pa­nied me on jour­neys through the Ama­zo­nian rain­for­est, across the Sa­hara, up the Zam­bezi and, some­what more pro­saically, along Offa’s Dyke, the Pen­nine Way and other Na­tional Trails.

I can’t say, in all hon­esty, that it’s en­tirely ac­cu­rate. More than once, I’ve cursed it—es­pe­cially the time I nearly found my­self cross­ing ac­ci­den­tally into the Su­dan—but I put up with its foibles as one puts up with the id­iosyn­cra­cies of an old friend. As Lord Bol­ing­broke said: ‘Truth lies within a lit­tle and cer­tain com­pass, but er­ror is im­mense.’

‘Truth lies within a lit­tle and cer­tain com­pass, but er­ror is im­mense’

A group of young sailors aboard the train­ing ship Arethusa re­ceiv­ing com­pass in­struc­tion. The boys came from a va­ri­ety of poor back­grounds

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