I take GPS for granted. I don’t use it that much personally, because I don’t tend to go anywhere, but I’m sure all this technology I love to use makes use of GPS. Thanks to GPS, we can forget that calculating longitude without the help of a network of satellites is difficult and requires great mathematical and engineering expertise. GPS might not be great at giving directions, but that doesn’t mean you’re lost.
In the days—centuries—prior to GPS, you could get lost. Really lost. I’m not sure how to describe how lost you could be, out there on the ocean, no longer in sight of shore. Latitude was relatively easy—well, easy enough once you dealt with the pitching deck, the storms, and the scurvy. Latitude corresponds both to the sun’s altitude in the sky (at noon) and to the altitude of certain stars (if you are in the Northern Hemisphere, Polaris is a good choice) at night. So you could figure out how far away from the equator or the poles. But how far away were you from the nearest charted island? And were you to the east of it, or the west?
Longitude, or rather the “starting point” for lines of longitude, is entirely arbitrary. The only way to calculate longitude is to measure the difference in time between two points: the reference point (e.g., 0° longitude) and your current location. That sounds easy enough: just take a watch with you that’s set to London time, and at noon at your current location, check what time the watch reports.
Much like our skill at flinging sophisticated pieces of technology into orbit has advanced, so too has our ability to construct watches. For the longest time, the solution to calculating longitude eluded mariners because no one could construct a clock that was both accurate enough and durable enough. The constant changes in pressure, humidity, and temperature played havoc with the fine mechanisms that allowed clocks to keep time. Without accuracy, a watch is useless as a method to calculate longitude.
This problem consumed great minds for centuries. It eventually came to a head in 1714, when the English Parliament authorized the creation of a Board of Longitude to disperse prizes for new ways of accurately calculating longitude. The grand prize was £20,000—or $12 million in today’s currency. Longitude was a big deal.
I knew the gist of the John Harrison story prior to reading Longitude, but Dava Sobel goes beyond the accomplishments of this single man and charts the course of the problem, and all its proposed solutions. She sets up a context against which the true scope and power of Harrison’s achievement might be measured. As I explained above, the general solution to calculating longitude was long in evidence, but no one could think of a way to effect it. Galileo had some good ideas related to his observations of Jupiter’s moon, but they were hardly practical for marine navigation. Later, Newton and other English scientists were convinced that astronomy held the key to calculating longitude—and the king agreed with them, establishing the Royal Observatory for the purpose of cataloguing the stars. More than a simple puzzle that made academics scratch their heads, the problem of longitude affected society and the economy. It drove scientific inquiry and technological innovation. Watching this unfold through Sobel’s storytelling is breathtaking and inspiring.
Harrison’s origins read like something out of a fairy tale or a superhero book. His father was a carpenter, and he was trained as a carpenter, not as a watchmaker. Yet this craft fascinated him, so he trained himself to build clocks. In fact, he built a clock entirely out of wood, a clock that required no lubrication owing to the way he had constructed it and the type of wood he had used. John Harrison was not just a tinker or dabbler; he was a creative genius. So he decided to solve the longitude problem. And he did. But when he went to London for his reward, he was met with scepticism, animosity, and belligerence. Thanks to the politics of London, the Board of Longitude was populated by representatives from the astronomy camp, and they were none too keen on Harrison’s mechanical marvel. For the rest of his life, Harrison would improve upon his prototype and receive stipends from the Board, but that recognition and prize money lay beyond his reach.
I personally think we tend to put too much stock in the “great individual” approach to history. I can see why it is appealing for stories, and for works of popular history: our ability to turn history into a biography boils away our dislike of dates and dry facts and lets us focus on the relationships and motivations of the characters. The central conflict of Longitude is not the need to calculate longitude but the antagonistic relationship between the Harrisons and the Reverend Maskelyne. Maskelyne championed the “lunar distance” method of calculating longitude. It just so happened, too, that later on in his life he became the Astronomer Royal, and therefore a member of the Board of Longitude. That didn’t go over well for Harrison’s chances at being awarded that prize.
Indeed, echoes of the great rivalries across the ages surface in Longitude, reminding us that science is never as simple nor as objective as we like to think. Invention is partly innovation, partly inspiration, and part imitation. Sobel is careful to stress that Maskelyne was not the villain in this piece, merely the antagonist—like the feud between Newton and Hooke, the feud between Harrison and Maskelyne was a dispute between two men who knew their stuff. But where ego is concerned and establishing primacy is often necessary for the money and prestige that follows a discovery, tempers will flare and harsh words will be exchanged.
So with this centuries-old problem juxtaposed against a feud between a rural carpenter-turned-watchmaker and the Astronomer Royal, Sobel turns Longitude from a history book into an exciting story. The trick to making any historical account interesting lies in exposing the details and connections that a casual reader, like myself, wouldn’t necessarily know. Sobel does this by charting the connections between Harrison and luminary contemporaries, including Isaac Newton, Edmund Halley, and Christopher Wren. She does this even with the considerable handicap of lacking much evidence about Harrison’s early life.
Sobel also goes into the intricate inner workings of Harrison’s successive marine chronometers. The genesis and evolution of the marine chronometer, particularly once it had spread to other watchmakers, gave us not only an accurate way to calculate longitude but other useful horological innovations! As Sobel describes the clever devices he designed to solve the limitations of sea clocks, all I could think was, “I have no idea what she is trying to say. This book could use pictures.” Lo and behold, as I reached the middle of the volume, I stumbled into the glossy inset that includes diagrams of a grasshopper escapement and photos of Harrison’s portrait and the chronometers H–1 through H–4. It’s amazing that these timekeepers (with the exception of H–4) continue to run today.
I wish Longitude were longer, but at the same time I love the size of the book as it is. My edition is a nice little paperback copy with a beautiful, high-quality cover. It is compact and deceptively slim for such an interesting history. Yet it is also definitely just a survey. I’m not sure, given the lack of details, how much longer Sobel could have spun it out. But the episodic nature of the chapters, and the abbreviated way she communicates the stories of the testing of H–3, H–4, etc., by Captain Cook and others, seems to indicate that there is more here to tell. Or is that another story?
Oh well. I really liked Longitude. It has the perfect mix of narrative, character, and scientific explanation to make it a fascinating work of history of science. Dava Sobel weaves a fascinating tale set against a problem centuries in the solving, one that vexed astronomers, clockmakers, and mariners alike but whose solution led to advances in all three fields. I, personally, rely on my GPS devices to find my longitude. But it’s good to know that if the GPS network ever goes down, there is at least one museum I can rob for some high-quality longitude calculation devices.
Now excuse me while I draw up some blueprints….