Kelly Prime

When Harrison finished H4, he didn't do what he'd done with his other inventions.

He didn't insist that this one wasn't right or ask for more time.

He was finally, finally ready to have his work tested and collect the Longitude Prize.

To take top prize, Harrison would need to bring H4 by sea to Jamaica and then on arrival take longitude calculations.

If the difference between Harrison's number and the real longitude of Jamaica was within 30 nautical miles or half a degree of longitude, he would at long last take home the prize.

In 1761, Harrison's son William traveled with H-4 all the way across the Atlantic Ocean on a two-month journey through icy cold, humid heat, and rolling seas.

He collected his data, which was accurate to about a single nautical mile, way closer than the 30-mile cutoff.

They sent him to Jamaica even though they weren't sure where Jamaica was.

This was insane behavior, a huge waste of time.

Obviously, the Harrisons were exasperated.

Harrison may have finally perfected his watch, but his timing was horrible.

It took him so long that by this point, most of his friends and allies on the board had retired or just straight up died.

The Board of Longitude was looking at Harrison and saying, this is a guy who's over 70 years old.

He'd taken decades to build one watch, and they weren't even sure he could make a second one, let alone put them in the hands of every captain trying to make their way across the open seas.

The Board of Longitude kept setting up new hoops for Harrison to jump through.

Harrison lost his patience, and he and his son William started publishing attacks against the board.

In the end, Harrison and his son decided to pull the boldest, most daring card they had up their sleeve.

They tattled.

In 1772, King George tested a copy of H4 called, you guessed it, H5, and was thoroughly impressed by its accuracy.

At the instruction of the king, Parliament awarded John Harrison the rest of the money he was owed as a thank you for his decades of work.