Compass opens with a cautionary tale of a modern mega-yacht nearly coming to grief because of the builder’s (and the owner’s) over-reliance on state-of-the-art electronic navigation. When the electronics failed, there was no way to navigate — which very nearly cost the unlucky sailors both the boat and their lives. Although the owner of the yacht made it back (and immediately had a magnetic compass installed) Compass is filled with many stories of much less fortunate mariners and the long struggle to produce a reliable and affordable marine compass.

As with the search for longitude, there were many false starts and centuries of experimentation before people finally got it right. Alan Gurney chronicles the many trials, errors, missteps, and outright buffoonery that eventually led to the modern magnetic compass so many of us (including me, until I read this book) now take for granted. What today can be purchased for a few dollars and is considered little more than a child’s toy by many was so very precious during the great age of sail that anyone caught tampering with it would have his hand pinned to the mast with a dagger.

While reading the book, one can’t help but wonder how mariners in the Age of Discovery ever found anything at all. Some of the finest minds in European history — Sir Isaac Newton, Edmond Halley (the discoverer of the comet that bears his name), and even Captain James Cook worked for years — and with limited success — on the problems of magnetic variation (changes in the Earth ‘s magnetic field) and deviation (compass error caused by magnetic attraction to metals near the compass itself). Until reading the book, I had no idea just how lost most people were for so many years.

Compass is an excellent historical, adventure, and even technical book — and manages to cover all three areas well. Although the book has a heavy British emphasis (naturally enough, since Britannia “ruled the waves” for so long) and deals primarily with naval and merchant vessels, the stories are just as applicable to small boats regardless of nationality. It would be an excellent addition to the onboard library (to read during a passage or at night while at anchor) or to have at home to develop an appreciation for what it took to develop the compass we so often undervalue. I, for one, will never look at my compass the same way again.

Compass: A Story of Exploration and Innovation By Alan Gurney (W.W. Norton & Company, 2004; 307 pages)