Timothy Rice


He wrested the world's whereabouts from the stars, and locked the secret in a pocket watch.

Rating: 3/5 – Decent enough, if the subject matter is interesting to you

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Longitude covers well, longitude. Particularly the issue of knowing your position at sea and the various attempts that were made up through the 1700s to solve the problem. Turns out that because the earth is round and spins this is actually a lot harder than it sounds.

More specifically, the book focuses on the great clockmaker John Harrison’s attempts to build a clock that could accurately tell time at sea. Because if you can keep accurate time, If you know the time at sea, at the time at another fixed location (say Greenwich, England) some simple arithmatic will produce your longitude. determining your longitude is a quite trivial matter. Traditional pendulum clocks are affected by the rolling motion of the ship, so can’t be used and a more clever solution had to be devised.

Harrison accomplished this incredible feat over four successive generations of timekeepers, culminating in his masterpiece H4, the first marine chronometer A timekeeper capable of keeping accurate time at sea. Marine chronometers were fixures aboard all naval vessels until they were gradually obsoleted by quartz (and later atomic) clocks and eventually the Global Positioning System (GPS). .

Again with this book I found the content lacking. Too much time spent on the drama of Harrison’s life and not enough devoted to his spectacular technical achievement. “What made H4 so special?” is apparently not a question the author felt needed asking. Indeed, finding any material about this is remarkably difficult. I think this is generally going to be the case with popsci books. They’re more about the people than the discoveries.

Hopefully I’ve learned my lesson this time, and will stick to more technical books in the future. In the meantime, if you’re really interested in the history of horology and navigation and can put up with a sparsity of technical details, you might enjoy this book.