Accurate Time

In the history of naval travel, it was easy enough to tell what latitude you’re at—just look at where the sun is in the sky at noon—but telling your longitude was actually a very difficult problem, and just as important as telling your latitude. In the 1700s the British government actually offered a serious cash prize for anyone who could devise a simple, practical way of figuring out one’s longitude. Ultimately, the winning strategy was a very precise clock, since if you know the exact time you can just look at your angle to the sun and calculating your longitude from that is easy.

The precise clock never actually won the prize, though. Why not turns out to be interesting, because the Longitude Committee was actually kind of reasonable in not awarding it.

In the 1720s clockmaker Henry Sully thought it would be possible to make a clock precise enough to do this. To give an idea of the problems to be overcome, watches were generally sensitive to temperature, which caused the metal in them to expand and contract, as well as other problems such as keeping time while being wound. Sully did come up with a highly accurate clock, but unfortunately his use of gravity to power it rather than a spring meant that the clock was only accurate in calm weather. Not a great plan for keeping time on seagoing ships.

In the 1730s John Harrison thought that he could do better, and worked on making more accurate clocks that worked even when jostled. Harrison developed several clocks over the next 30 years which earned enough prizes to keep working on his designs, but it was only with his fourth attempt, “H4”, finished in 1760, that he finally had a clock that would work. It was tested on several long sea voyages and found to be accurate to within a few seconds over the course of months, which translated into a longitude accuracy of about 10 miles. This was a fantastic result, and Harrison applied for the prize.

So why didn’t he get it? Well, it took six years to build H4 and it cost £400 at a time when an entire ship cost about £1,200 pounds. It worked, to be sure, but was it really practical? It was phenomenally expensive and took a very long time to build. Granted, his next sea watch, H5, only took about three years to build, this is still a very long time for skilled craftsmen to be working. There are only so many skilled watchmakers in England, after all.

To be fair, Larcum Kendall (another watchmaker) was asked by the Longitude Board to copy H4 and did so in far less than six years, though at a cost of £450. Kendall went on to make other, simplified copies that cost less money but didn’t work as well.

The other thing is that a competing methodology, the lunar distance method, was also being tried out at the time. It relied on having tables of extremely accurate measurements of the moon’s motion, which were made, and one could compare the position of the moon to the sun in order to figure out one’s longitude. It was tested and worked, though it was about a third as accurate as H4 (i.e. correct to within 30 miles compared to H4’s 10) and required difficult calculations to be carried out on board the ship. On the other hand, it was way cheaper and with the printing press having been invented back in the 1400s, the tables could be copied way faster than one per several years.

So what happened, that accurate watches won but Harrison didn’t win the prize?

Basically, Harrison’s watches were great but way too difficult to make and way too expensive to be actually practical. Some were in fact made. For example, James Cook used K1 (the first copy of H4 made by Kendall) during his famous voyages in the Pacific ocean. There aren’t records of many being made, though. What happened is what often happens in the adoption of technology—after a while, people got better at making them, and making them cheaper. This wasn’t all the development of watch technology, by the way. Metallurgy played a roll, for example, as metals with better properties were developed that allowed greater accuracy at lower cost.

That’s not to say that improvements in watch technology didn’t play a roll. In the 1780s, John Arnold developed a simpler design that, unlike Kendall’s simplifications, kept time as accurately. Once his patents expired in the 1790s, other watchmakers could copy his designs, bringing the cost of accurate clocks (or “chronometers”) down further. When chronometers cost between £25 and £100 pounds, their use became extremely common because they provided enough benefit (including ships not being lost at sea or running aground in the dark because they don’t know where they are).

So why didn’t the prize ever get awarded? By the time it was clear that chronometers were the winning solution to the problem of longitude, they had already been solving it for a while, and that was due to a lot of people bringing the costs down over time, bit by bit. There wasn’t any person you could really point to as being the one who did it.

That said, Harrison was not left empty handed. Over the course of the thirty-plus years he worked on the problem, he was awarded, in total, £23,065. Not bad at a time when a ship might cost £1,200.

This is often the way technology develops; one person comes up with the idea, another makes it work, and then an army of people make it practical. When we remember anyone, we tend to remember the guy who was the first to make it work. A lot of credit goes to the people who made it practical, though.

Which is not to say that we should feel sorry for the people no one remembers who made the technology practical. They were generally well paid for their labor, and if they rarely become rich, they usually can support themselves and their family in comfort, which is what most people labor for anyway. There are more important things in life than money and fame.

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