Sextant: A Voyage Guided by the Stars and the Men Who Mapped the World's Oceans

In the tradition of Dava Sobel's ‘Longitude’ comes sailing expert David Barrie's compelling and dramatic tale of invention and discovery – an eloquent elegy to one of the most important navigational instruments ever created, and the daring mariners who used it to explore, conquer, and map the world.

This is the story of an instrument that changed the world. In prose as crisp as the book’s subject, David Barrie tells how and why the sextant was invented; how offshore navigators depended on it for their lives in wild and dangerous seas until the advent of GPS – and the sextant’s vital role in the history of exploration. Much of the book is set amidst the waves of the Pacific Ocean as explorers searched for the great southern ocean, charted the coasts of Australia, New Zealand, Canada, Alaska as well as the Pacific islands. Among the protagonists are Captain James Cook, the great French navigator, La Pérouse, who built on Cook's work in the exploring the Pacific during the 1780s, but never made it home, George Vancouver, Matthew Flinders – the first man to circumnavigate Australia, Robert FitzRoy of the Beagle, Joshua Slocum, the redoubtable old ‘lunarian’ and successful pilot of a small boat across the wild Southern Ocean and Frank Worsley of the Endurance.

Their stories are interwoven with the author’s account of his own transatlantic passage aboard Saecwen in 1973, using the very same navigational tools as Captain Cook, and the book is infused with a sense of wonder and dramatic discovery.

A heady mix of adventure, science, mathematics and derring-do, ‘Sextant’ is a timeless tale of sea-faring and exploration. A love letter to the sea, it is narrative history for star gazers and sailors, for everyone with a love of salty breezes and a sense of adventure. Beautifully produced, ‘Sextant’ offers storytelling at its very best.

David Barrie

The Story Behind Sextant

The story of Sextant began in 1973 when a family friend - Colin McMullen - asked me to help him sail his 35-foot yacht back across the Atlantic from America. I was nineteen and it was such an exciting offer that I immediately accepted. After cruising up the coast of Maine, we set sail from Halifax, Nova Scotia, at the end of July.

In those days the only one safe way to navigate a small boat across an ocean was with a sextant to measure the heights of the sun and stars above the horizon. You also needed a chronometer to determine the exact time of each sight. This was exactly how Captain Cook navigated back in the 1770s.

I learned a lot during that 24-day voyage, and not just about celestial navigation. I was sometimes frightened, often cold, wet and uncomfortable, but there were also many moments of delight and exaltation. The majestic spectacle of the black immensity of the night sky sparkling from horizon to horizon with the undimmed light of countless stars was astounding. And to fix your position in mid-ocean by the light of the sun and stars is a truly sublime experience.

So one of my aims in writing this book was simply to tell the story of that life-changing voyage, of how I learned to use a sextant. Also 1973 was the year the US armed forces began developing the satellite navigation system we now know as GPS. At its heart is a network of satellites in precisely determined orbits each carrying its own atomic clock. A GPS receiver picks up the faint signals from these satellites and a computer chip uses them to determine its position. Since 2000 anyone with a GPS receiver has been able to fix his or her position to within a few meters.

The golden age of celestial navigation has now come to an end, but for two hundred years or more the sextant was an indispensable navigational tool. So my second aim is to celebrate the achievements of the mathematicians, astronomers and instrument-makers who made this great navigational breakthrough possible, and to illuminate the crucial role the sextant played in it.

I also wanted to commemorate the extraordinary men who put the sextant to such good use in exploring and mapping the world. Some, like Cook, are still famous but many have been almost forgotten. I tell the remarkable tales of just a few of these heroic mariners - including Bougainville, La Pérouse, Vancouver, Flinders and FitzRoy.

And I could not resist including accounts of three astonishing small boat voyages - by William Bligh, Joshua Slocum and Frank Worsley - the success of which depended on accurate celestial navigation. Sextant is an elegy to a technology that has now all but vanished.

It shows how much we owe to this elegant instrument and to the courageous people who used it. And I hope it also gives some sense of how rewarding it is to fix your position on the open ocean by reference to the heavens above - rather than just by pushing a button.