The Quest for Precision: Unveiling the Secrets of Longitude


Longitude, written by Dava Sobel, is an enthralling non-fiction book that delves into the captivating story of the race to solve one of the greatest scientific and navigational problems of the 18th century. Through meticulous research and a compelling narrative, Sobel unveils the incredible journey undertaken by John Harrison, a self-taught clockmaker, as he fights against the prevailing belief that determining longitude at sea was an unattainable task. Sobel, an accomplished writer and former science reporter for The New York Times, skillfully interweaves historical events, personal anecdotes, and scientific discoveries to shed light on an often overlooked but critical aspect of our modern globalized world.

Chapter 1: Introduction to the Problem

Chapter 1: Introduction to the Problem provides an insightful overview of the book Longitude by Dava Sobel. The chapter starts by introducing the historical context of the 18th century when ships were the primary mode of transportation across the vast oceans. Navigating accurately at sea was a persistent challenge as sailors struggled to determine their longitude, or east-west position, which led to countless shipwrecks and losses of human life.

Sobel then highlights the significance of longitude for the advancement of global exploration and trade, as well as the detrimental consequences of its unknown nature. She discusses the prestigious British scientific competition held in 1714, offering a prize of £20,000 (equivalent to millions today) to anyone who could devise a reliable method to measure longitude accurately.

The chapter introduces the main characters and their contributions to the “longitude problem.” Sobel introduces John Harrison, a skilled clockmaker obsessed with constructing a timepiece capable of maintaining accurate marine timekeeping. Harrison represents a revolutionary approach to solving the problem by developing the marine chronometer.

The rival methods proposed by astronomers and mathematicians are discussed, presenting the difficulties and limitations of celestial navigation using the moon or the positions of celestial bodies. Sobel emphasizes the controversy surrounding the longitude problem, with different factions arguing for their own proposed methods.

Finally, the chapter highlights the significance of this problem for the British Empire’s maritime dominance and the urgency to find a solution. It sets the stage for the subsequent chapters, which delve into the personal challenges, triumphs, and controversies involved in the pursuit of the longitude solution throughout the book.

Chapter 2: John Harrison’s Early Life

Chapter 2 of the book “Longitude” by Dava Sobel details the early life of John Harrison, a British clockmaker and inventor. Born in the village of Foulby, Yorkshire, in 1693, Harrison hailed from a humble background. He was the first of five children and was raised on a small farm. Despite limited access to education, Harrison’s mechanical aptitude became evident at an early age.

Harrison’s interest in creating precise timekeeping devices emerged when he noticed the inaccuracy of the existing methods used to determine longitude at sea. The dominant method, known as dead reckoning, relied on estimating a ship’s position based on the last known latitude and the ship’s speed and direction. However, this method often led to disastrous navigational errors.

Recognizing the need for accurate timekeeping to solve the longitude problem, Harrison began to experiment with clocks. He invented a wooden pendulum clock, which, despite its inaccuracies, demonstrated his determination to solve the problem. Harrison’s perseverance led to his father sending him to Barrow-on-Humber to study under a skilled carpenter and clockmaker named Henry Hindley.

Under Hindley’s tutelage, Harrison honed his clockmaking skills and expanded his knowledge of mechanical systems. He experimented with creating clock mechanisms that would withstand the motions of a ship, which were notorious for causing inaccuracies in timekeeping instruments. These experiments laid the foundation for Harrison’s groundbreaking creation, the marine chronometer.

This chapter highlights John Harrison’s early life and the development of his interest in precise timekeeping. It provides insight into his humble beginnings, his fascination with the longitude problem, and his commitment to finding a solution. Sobel sets the stage for Harrison’s future accomplishments as she delves into the challenges he faced and the skills he honed during his formative years.

Chapter 3: The Longitude Prize

Chapter 3 of “Longitude” by Dava Sobel, titled “The Longitude Prize,” delves into the establishment of the Board of Longitude and their subsequent decision to offer a substantial monetary award for the solution to the longitude problem.

The chapter opens with the lamentations of seamen who suffer from the lack of an accurate method to determine longitude at sea. Sobel highlights how mariners have relied on guesswork, dead reckoning, and crude instruments that often led to disastrous consequences.

Amidst this backdrop, Sobel introduces an esteemed Englishman named Jeremy Thacker, a skilled technician who developed an intricate mechanical solution: the “Longitude Timekeeper.” Despite considering Thacker’s invention, the Board of Longitude, a group of influential scientists, astronomers, and government officials, deemed it unimpressive and unworthy of their support.

Sobel then shifts focus to John Harrison, a self-taught clockmaker who dedicated his life to solving the longitude problem. Harrison’s innovative timepieces had already proven their accuracy on shorter voyages, but he eagerly sought recognition and support from the Board. Despite his numerous applications, the Board showed little interest in his work.

Recognizing the urgent need for a solution, King George III himself intervened. He proposed a royal proclamation creating the Longitude Prize, a significant monetary incentive for anyone who could deliver a reliable method for determining longitude at sea. The prize offered £20,000, an astronomical sum at the time, equivalent to millions of pounds today.

The chapter concludes with the establishment of a series of guidelines and challenges for winning the prize, including the requirement that the proposed solution be accurate within 30 nautical miles on a six-week voyage. The Longitude Prize sparked newfound hope, motivating inventors, astronomers, and mathematicians to explore ingenious methods, ultimately leading to a search for an accurate clock mechanism to solve the longitude problem.

In summary, Chapter 3 of “Longitude” introduces the catalyst for the search for a solution to the longitude problem: the establishment of the Longitude Prize. It highlights the rejection of Thacker’s timekeeper, honors Harrison’s innovative efforts despite the Board’s skepticism, and emphasizes the potential transformative power of the prize, which would spark a flurry of inventive and groundbreaking ideas in the quest for an accurate method of determining longitude at sea.


Chapter 4: John Harrison’s Marine Chronometer

Chapter 4: John Harrison’s Marine Chronometer delves into the life and work of John Harrison, who emerged as a significant figure in the quest for determining longitude at sea. Dava Sobel highlights the challenges faced by sailors due to the absence of an accurate timekeeping device in the 18th century.

Born into a humble family in Yorkshire, John Harrison exhibited a keen interest in clocks and timekeeping from a young age. He combined his natural talent with mechanical aptitude to design and construct an innovative clock which he called the “sea-watch.” This early version of a marine timekeeper was aimed at accurately measuring time at sea, enabling sailors to determine their longitude.

Harrison faced multiple obstacles in his pursuit of creating a reliable timepiece. The harsh marine environment, which involved extreme temperatures, humidity, and constant motion, required his clock to be resistant to these conditions. Harrison’s first attempt, known as H1, proved to be a failure, as it lacked the necessary precision and robustness.

Undeterred, Harrison continued to refine his designs, devoting several years to his work. His groundbreaking invention, H4, brought significant advancements to marine timekeeping. The timepiece utilized a novel balance mechanism and was encased in a mostly wooden structure to account for the challenges posed by the sea.

Sobel notes that Harrison’s chronometer underwent rigorous testing, including a sea voyage to Jamaica, where it successfully maintained its accuracy even in treacherous conditions. The marine chronometer proved crucial in determining longitude precisely and revolutionized navigation, making travel safer and more efficient.

In Chapter 4 of Longitude, Dava Sobel emphasizes John Harrison’s tireless dedication to overcoming technical obstacles and his pivotal contribution to solving the longitude problem.

Chapter 5: The Quest for Recognition

In chapter 5 of the book “Longitude” by Dava Sobel, the focus shifts to John Harrison’s relentless pursuit of recognition for his groundbreaking invention, the marine chronometer. Harrison’s invention was a revolutionary timekeeping device that could accurately determine a ship’s longitude at sea. However, despite its immense potential for saving countless lives and preventing maritime disasters, Harrison faced numerous obstacles in gaining recognition for his invention.

Initially, Harrison embarked on the path of securing a monetary reward through the Board of Longitude, a British organization offering a prize for the solution to the longitude problem. However, the Board’s members were skeptical of Harrison’s chronometer, as it greatly deviated from the traditional methods of determining longitude involving astronomical observations. They also doubted its reliability, raising concerns about its ability to withstand the harsh conditions of sea voyages.

Undeterred, Harrison persisted in improving his chronometer’s design, refining its technology to enhance accuracy and durability. He constructed multiple versions, each one more sophisticated and efficient than its predecessor. Over the years, Harrison’s relentless dedication to his invention bore fruit as he successfully created marine timekeepers capable of surpassing the required accuracy by the Board.

However, Harrison soon faced a new set of challenges as the Board subjected his chronometers to a series of arduous sea trials. The tests aimed to determine the device’s reliability under real-world conditions. Unfortunately, the Board’s treatment of Harrison seemed unfair, as they subjected him to long delays, continuous scrutiny, and even attempts at reverse engineering his invention.

Although Harrison’s chronometers consistently performed remarkably well during the sea trials, his battle for recognition continued. The Board questioned the practicality and affordability of mass-producing the chronometers, ultimately denying him the full reward. Frustrated and disillusioned, Harrison resorted to publishing a detailed account of his chronometer’s construction to defend his invention.

The quest for recognition portrayed in Chapter 5 highlights Harrison’s determination, resilience, and continuous fight against the established scientific and bureaucratic system. His tireless efforts laid the foundation for future advancements in timekeeping and improved navigation, eventually leading to the accurate determination of longitude at sea.

Chapter 6: Harrison’s Later Innovations

Chapter 6 of “Longitude” by Dava Sobel, titled “Harrison’s Later Innovations,” delves into the further progress and innovations made by John Harrison in his pursuit to solve the problem of determining longitude at sea.

Sobel begins by highlighting Harrison’s struggle to gain recognition and support for his earlier marine timekeepers. Frustrated with the lack of recognition, Harrison decided to take matters into his own hands and traveled to London to present his first timepiece to the Royal Society. Despite skepticism, Harrison’s meticulous craftsmanship and dedication to solving the longitude problem impressed some members of the Society, including mathematician and astronomer Nevil Maskelyne.

In this chapter, Sobel focuses on Harrison’s development of his second marine timekeeper, H2. Harrison aimed to improve upon the flaws of his first timepiece, H1, by constructing a lighter and more portable instrument. The central innovation of H2 was a system of circular arcs, or “curvilinear” motions, which reduced the friction within the timekeeping mechanism. This allowed the clock to maintain accuracy even in the rough conditions of a ship at sea.

Sobel highlights the challenges faced by Harrison, including financial constraints and the lengthy process of building a second timekeeper from scratch. Nonetheless, despite various setbacks and delays, Harrison’s never-wavering determination propelled him forward.

The chapter concludes with a turning point in Harrison’s journey. After years of refining H2, he finally presented it to the Board of Longitude. Though the board had initially expressed their support for Harrison, they proposed a series of further trials for the timepiece, which left him disheartened. However, the chapter ends on a hopeful note, as Harrison receives news that Maskelyne has taken the responsibility of testing H2 by accompanying Captain Cook on his next expedition.

In summary, Chapter 6 of “Longitude” follows the ongoing journey of John Harrison as he continues his pursuit of crafting and perfecting marine timekeepers. Despite numerous obstacles, Harrison’s unwavering commitment to this cause drives him to create his second clock, H2, incorporating innovative curvilinear motion. While faced with new challenges from the Board of Longitude, Harrison’s dedication ultimately leads to an opportunity for his timepiece to be tested during Captain Cook’s expedition.


Chapter 7: Trial and Triumph

Chapter 7 of the book “Longitude” by Dava Sobel, titled “Trial and Triumph,” revolves around the life and achievements of John Harrison, an English clockmaker. Harrison, fascinated by the problem of measuring longitude at sea, dedicated his life to solving this complex issue.

The chapter begins by describing Harrison’s background as the son of a carpenter and his early inclination towards mechanical devices. Harrison becomes an apprentice to a clockmaker and develops his skills in precision timekeeping. Recognizing the importance of accurate timekeeping for navigation, he sets out to create a timepiece that can withstand the motion and fluctuations of a ship at sea.

Harrison’s first major breakthrough comes in the form of a clock known as H1. Built entirely of wood, it successfully compensates for changes in temperature and humidity. However, the Longitude Board, responsible for solving the longitude problem, dismisses this invention due to their skepticism towards nontraditional materials.

Undeterred, Harrison spends years refining and improving his design, resulting in the creation of H4, a compact chronometer. Its innovative features, including bimetallic strips to counteract temperature changes and a unique escapement mechanism, allow it to keep accurate time at sea. Despite facing numerous obstacles, including the distrust and skepticism of the Longitude Board, Harrison’s unwavering determination drives him to present H4 to the board, hoping it will finally earn him recognition and reward.

Through detailed accounts and anecdotes, Sobel illustrates the immense challenges Harrison faced in his quest for accurate longitude measurement. The chapter captures both the trials and triumphs of Harrison’s journey, emphasizing his relentless pursuit of innovation and dedication to solving the longitude problem.

Chapter 8: Legacy and Impact

Chapter 8 of Dava Sobel’s book “Longitude” explores the lasting legacy and impact of John Harrison’s development of the marine chronometer. The chapter highlights how Harrison’s invention revolutionized navigation and contributed to significant advancements in science and technology.

Sobel begins by acknowledging how Harrison’s chronometers transformed the way sailors determined their longitude at sea. Prior to Harrison’s breakthrough, sailors heavily relied on celestial navigation, which was often unreliable and imprecise. The introduction of the chronometer allowed sailors to accurately measure time, enabling them to calculate their longitude with much greater accuracy. This advancement not only improved navigation, but also increased the safety and efficiency of sea travel.

Sobel also explains how Harrison’s work greatly influenced the field of horology, the study of timekeeping devices. His chronometers became the precursor to modern-day wristwatches and precision timekeeping instruments. Furthermore, Harrison’s innovative use of various materials, as well as his mastery of precision engineering, set new standards in craftsmanship and design.

The chapter also discusses the broader impact Harrison’s invention had on science and society. Scientists, engineers, and inventors were inspired by Harrison’s accomplishment and began applying his principles and techniques in their own work. The quest for accurate timekeeping quickly spread throughout the world, leading to the establishment of observatories and the development of more sophisticated timekeeping devices.

Additionally, Sobel highlights the significance of Harrison’s story in challenging traditional thinking and established authorities. Harrison faced numerous obstacles and skepticism throughout his journey, but his determination to prove the accuracy and reliability of his chronometers ultimately triumphed. His success demonstrated the importance of tenacity, perseverance, and empirical evidence in advancing scientific knowledge.

In summary, Chapter 8 of “Longitude” illustrates how John Harrison’s marine chronometer revolutionized navigation, inspired advancements in horology, influenced scientific research, and challenged conventional wisdom. His invention and achievements continue to be celebrated as groundbreaking contributions to the world of timekeeping and maritime exploration.

After Reading

In conclusion, “Longitude” by Dava Sobel is a fascinating account of the quest to solve one of the greatest challenges faced by sailors – determining their exact position at sea. Sobel expertly weaves together the stories of two men, John Harrison and Nevil Maskelyne, who played pivotal roles in the development of a reliable method for measuring longitude. Through their tireless efforts and ingenuity, they ultimately revolutionized navigation and forever changed the course of history. Sobel’s book not only provides a comprehensive understanding of the longitude problem but also sheds light on the power of determination and human innovation. Overall, “Longitude” is a captivating and enlightening read for anyone interested in the intersection of science, history, and exploration.

1. “Sapiens” by Yuval Noah Harari

– This book offers a compelling narrative of human history, exploring our species’ journey from the Stone Age to the modern era. It delves into the impact of cognitive, social, and technological revolutions on our evolution, providing a thought-provoking perspective on our place in the world.

2. “The Immortal Life of Henrietta Lacks” by Rebecca Skloot

– This true story sheds light on the incredible scientific advancements achieved through the HeLa cell line, taken without consent from a poor African American woman named Henrietta Lacks in the 1950s. It explores ethical dilemmas, race, and our understanding of medical ethics in an engaging and compassionate manner.

3. “The Ghost Map” by Steven Johnson

– This gripping historical account explores the devastating 1854 cholera outbreak in London, focusing on the investigations of physician John Snow and Reverend Henry Whitehead. In examining the origins and spread of the disease, it highlights the importance of epidemiology and public health in shaping modern society.

4. “The Gene” by Siddhartha Mukherjee

– In this profound book, Siddhartha Mukherjee takes readers on a journey through the history and implications of the “gene.” It skillfully intertwines personal anecdotes, scientific discoveries, and ethical dilemmas, providing a comprehensive exploration of genetics and its role in shaping human life and identity.

5. “The Sixth Extinction” by Elizabeth Kolbert

– This eye-opening book delves into the ongoing mass extinction currently affecting the Earth’s biodiversity. Elizabeth Kolbert explores the ways in which human activities, particularly climate change and habitat destruction, have contributed to the accelerated loss of species. It serves as a wake-up call, urging readers to reflect upon our responsibilities and the impact of our actions on the planet.

These five books cover a diverse range of topics, including history, science, genetics, epidemiology, and social implications. Each offers a unique perspective on our understanding of the world and ourselves, inviting readers to delve deeper into the complex and fascinating aspects of life and humanity.


  1. Pingback: Unlocking the Dark Side of Grocery Store Staples: Salt, Sugar, Fat - Booksplease

  2. Pingback: Exploring the Universe: Stephen Hawking's Brief Answers to the Big Questions - Booksplease

Leave a Reply

Your email address will not be published. Required fields are marked *