"An account of the man who developed the technology which allowed sailors to determine their longitude at sea. If you don't know where you are, it's hard to know where you're going, whether you've gotten there or if you've missed your target. If, while sailing around the Pacific Ocean, you need to navigate toward some small island to find food and water, grievous things can happen if you're wrong. And grievous things did happen.
Dava Sobel's book is an account of John Harrison, who spent his life (in the eighteenth century) perfecting a timepiece which was accurate to seconds in various climatic conditions ? moisture, barometric pressure, etc. ? all of which prior to that time had imposed serious technical limitations. You couldn't put a clock on a ship in those days because the ship pitched so much it would throw off the mechanism or destroy it entirely. You needed, basically, the perfect pocket watch, which Harrison invented. It was a thing of beauty as well as a huge leap forward technologically. The famous minds of that generation all thought the answer to determining longitude would be found in the stars, by using the sky as a map. Harrison believed the answer would be mechanical, and to find it he had to solve metallurgical problems as well as miniaturization problems, all of which he did in a small workshop in a remote part of England, competing for a prize from the King when the odds were stacked heavily against him."