The Explainer General
Where am I? This was a cruel question for sailors before John Harrison.
In 1707 a fleet of British warships mistook their location and sailed onto the rocky Scilly Islands. Two thousand men drowned. The Royal Navy offered a prize of £20,000 (3 to 4 million dollars in today’s money) for anyone who could provide a way for ships to find their position.
North and south latitude wasn’t the problem. Tables gave the positions of the sun, moon and stars above or below the equator. Navigators could use a sextant (it measures angles between the ocean horizon and a celestial body) to find a ship’s position north or south. But the only way of knowing your position on the spinning earth, east or west, is to know what time it is, within seconds, at the Royal Observatory at Greenwich, England—0° longitude.
Sailors needed a seagoing clock!
Clocks in the 1700’s were slow or fast by several minutes a week. Not good enough. And they measured seconds with a pendulum, which wouldn’t work on a rocking, rolling ship.
John Harrison was a fine carpenter who became fascinated by accurate timekeeping. He built big clocks for houses, barns and churches. Bit by bit he made them more accurate. He set out to win the longitude prize.
He invented ways for a clock to compensate for temperature, so they wouldn’t run slower when it got warmer. He invented a nearly frictionless escapement (the mechanism that “counts” the tick-tocks with the clock’s hands). He overcame the pendulum problem with pivoted “dumbells” that rocked back and forth with springs.
Harrison worked for five years to construct the large and beautiful Sea Clock #1. In 1736 Harrison and his clock took a trip on HMS Centurion to Lisbon, Portugal, and back. Harrison was terribly seasick. His clock was not. It was a great success.
But the Royal Navy wouldn’t award the prize. It dithered for the next 37 years. Harrison worked on, making his sea clocks smaller and more accurate. In 1761 he sent his son William on a trial run with Sea Watch #1 to Jamaica and back. The smaller clock worked beautifully. The Navy kept dithering.
Not until Harrison was 80 years old was part of the prize awarded to him. He died three years later but he knew that he had changed the world, solving one of our most important, most perplexing problems: where are we?
An important part of Jan Adkins' considerable output is books of non-fiction for young people, his special audience. He also writes humor and feature articles for several magazines. He has illustrated most of his books and contributes illustrations to dozens of mainstream magazines, especially on marine and technical subjects. Have a look at his Wooden Ship: The Building of a Wooden Sailing Vessel in 1870, a chronicle of a fictional whale ship describing and illustrating the details of her building from design to launching.
Jan Adkins is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.
MLA 8 Citation
Adkins, Jan. "Tick Tock: A Carpenter Solves an Ocean Riddle." Nonfiction Minute,
iNK Think Tank, 19 Mar. 2018, www.nonfictionminute.org/
Celebrating the History of Science
and the Science behind History
A common punishment for those accused of a crime in seventeenth century Europe was to be sent to the galleys. That meant spending the rest of your life at an oar in the dark, stinking hold of a ship.
Wind and oars were the only known propellant of the age. Paid employment at the oar had been tried and dismissed. The only reliable way to produce the necessary speed and endurance to chase down (or escape from) enemy ships or Barbary pirates was to use the whip on your oarsmen, something that didn’t go over well with paid employees. But as condemned criminals were plentiful in that era, it wasn’t difficult to find oarsmen.
When in 1685 Louis XIV revoked the Edict of Nantes—a law passed by his grandfather Henry IV that had ensured the freedom of Protestant worship in France—many French Protestants (known as Huguenots) who tried to flee the country were sent to the galleys.
What was life like as a galley slave? We know something about it from letters and memoirs of Huguenot convicts.
After a long and often grueling march to the ports, the convicts would be sorted into groups of five—these would become the people with whom one would eat, sleep, and work, often until one died of old age or overwork or both. Each group of five men manned an eighteen-foot oar–and there might be fifty oars on a ship. The convicts remained chained to their places. With each stroke, they had to rise together and push the oar forward, and then dip it in the water and pull backward, dropping into a sitting position. During battle, rowers might be required to maintain full speed for twenty-four hours straight, and be fed biscuits soaked in wine without pausing in their exertions. Those who died—or lost consciousness—were thrown overboard.
Horrific, yes. But there were at least some brief respites from the wretched existence, periods of time when the wind’s sails propelled the ship and the rowers could rest. And when the ship overwintered in port, the life of a gallérien became almost tolerable. They had room to lie down and sleep. Many gallériens learned to knit, and others were already skilled wig makers, tailors, and musicians—and were allowed to employ their trades in rotating weeks ashore.
In his memoirs, a Huguenot named Jean Marteilhe wrote about his capture in 1701 as a boy of 17, and his experiences as a galley slave having been chained together with other deserters, thieves, smugglers, Turks and Calvinists for 6 years from 1707 to 1713. His account is entitled Memoirs of a Galley Slave of the Sun King.
Sara Albee's book Why'd They Wear That? is published by National Geographic. Get ready to chuckle your way through centuries of fashion dos and don'ts! In this humorous and approachable narrative, you will learn about outrageous, politically-perilous, funky, disgusting, regrettable, and life-threatening creations people have worn throughout the course of human history, all the way up to the present day. For more information, click here.
MLA 8 Citation
Albee, Sarah. "Row, Row, Row Your Boats." Nonfiction Minute, iNK Think Tank, 22
Mar. 2018, www.nonfictionminute.org/the-nonfiction-minute/
For Vicki Cobb's BLOG (nonfiction book reviews, info on education, more), click here: Vicki's Blog
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