Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time

FOREWORD-CHAPTER 5

Reading Check

1. In Neil Armstrong’s Foreword, he notes that the prime meridian runs through Greenwich Observatory in the UK. (Foreword)

2. “The Equator. The Ecliptic. The Tropic of Cancer. The Tropic of Capricorn. The Arctic Circle. The prime meridian.” (Chapter 1)

3. A prize offered “for a ‘Practicable and Useful’ means of determining longitude” (Chapter 1)

4. “He invented a clock that would carry the true time from the home port, like an eternal flame, to any remote corner of the world.” (Chapter 1)

5. Dead reckoning (Chapter 2)

6. A combination compass and clock (Chapter 3)

Short Answer

1. Ptolemy was one of the first cartographers to plot latitude and longitude lines on his map. He used science to plot the major “imaginary lines”; however, he chooses himself to place the prime meridian at the Fortunate Islands (i.e., Canary Islands). (Chapter 1)

2. While latitude is fixed by science, longitude is difficult, particularly at sea, without modern technology. As the lack of longitudinal exactitude resulted in the casualties and the failures of many ships during the Age of Exploration, many European governments sought to find solutions to the problem by establishing observatories and funding various studies. (Chapter 1)

3. The lack of ability for countries to establish the longitudinal line had tremendous burdening costs for explorers. In particular, long voyages resulted in higher deaths of sailors from lack of nutrients. Economically, most ships were forced to follow the same trade routes, which resulted in higher pirating and more loss of life and cargo. (Chapter 2)

4. With prior attempts to track the motion of the moon lacking in more knowledge, Galileo began to track the motion of Jupiter’s moons which mariners could then set a watch to in order to determine their longitudinal placement. Galileo submitted his hypothesis to the King of Spain, along with a special headgear called “celatone.” While his method had some inaccuracies when used at sea, the Jovian satellites were used by other scientists for their own methods. (Chapter 3)

5. The idea of using clocks and watches was another popular idea during the 16th century; however, one of the main issues was that clocks often lost time, therefore losing their exactness. Christiaan Huygens, an astronomer and “the first great horologist” developed a pendulum clock for marine use, which still possessed flaws in determining exact longitude. (Chapter 4)

CHAPTERS 6-10

Reading Check

1. 60 nautical miles (Chapter 6)

2. A “chronometer” (Chapter 6)

3. It was constructed almost entirely of wood. (Chapter 7)

4. Because Halley published his star catalogues without his consent (Chapter 8)

5. The “clock of heaven” (Chapter 9)

6. The Copley Gold Medal (Chapter 10)

Short Answer

1. The Longitude Act (1714) offered the following three prize categories: “£20,000 (the equivalent of millions of dollars today) for a method to determine longitude to an accuracy of half a degree of a great circle; £15,000 for a method accurate to within two-thirds of a degree; £10,000 for a method accurate to within one degree.” The act established a Board of Longitude to determine the winners. (Chapter 6)

2. The large amount of prize money translated to mass submissions of entities for the prize, many of which were not about the subject of longitude at all. As a result, the quest for longitude “became a synonym for attempting the impossible” as well as a point of humor; even novels such as Gulliver’s Travels mentioned the search for longitude. (Chapter 6)

3. John Henderson was a carpenter in the north of England who was a self-taught horologist and inventor of precise timekeeping methods in clocks. After inventing both the precision methods of both the “gridiron” and the “grasshopper,” Henderson decides to travel to London and present his inventions to the Board of Longitude. (Chapter 7)

4. “Harrison’s No. 1” (i.e., H-1) was the first of three versions of a clock that could be used to determine the precise location of a ship. Both Edmund Halley and George Graham were supportive of Harrison’s project, and he was introduced first to the Royal Society and then to the Board of Longitude. After a series of tests that were required for the reception of the prize, Harrison himself was unhappy with the results, and spent the next several decades devising an H-2 and H-3 version. (Chapter 8)

5. Harrison’s approach represented a mechanical solution to finding longitude, while the “clock of heaven,” or celestial method, was advocated by mathematicians and astronomers. “Hadley’s quadrant” (also referred to as an “octant”) was one of the main inventions in the mid-18th century that advanced the celestial solution to the longitudinal problem. (Chapter 9)

6. After many years of submissions, with the support of his son, Harrison’s H-4 submission won the Longitude prize. Sobel notes that the H-4 was similar to a watch that Harrison received from horologist John Jeffreys, as the H-4 was a sleeker and lighter version of his H-1 invention. (Chapter 10)

CHAPTERS 11-15

Reading Check

1. The transit of Venus (Chapter 11)

2. There is no H-4 model in the oil painting. (Chapter 12)

3. Sauerkraut (Chapter 13)

4. King George III (Chapter 13)

5. “[C]hronometer” (Chapter 14)

6. “Nevil Maskelyne, fifth Astronomer Royal” (Chapter 15)

Short Answer

1. Sobel introduces Maskelyne as the “personif[ication of] the lunar distance method.” Together with James Bradley, another advocate of the celestial method, they challenged the accuracy of Harrison’s clock; in fact, Bradley’s position on the Board of Longitude provided barriers against Harrison winning the full prize money and made him redo his test sail. (Chapter 11)

2. The Board of Longitude began a set of negotiations with Harrison, forcing him to provide the drawings and explanations of his inventions before receiving the rest of his prize money. Matters were worsened after Maskelyne was announced the head of the Astronomer Royal, and as a final blow, Harrison was forced to have his inventions sent to Maskelyne for further testing. (Chapter 12)

3. After a series of tests, Maskelyne determined that there were too many flaws in the accuracy of the H-4 for it to be used alone, although it might be used together with other observations. (Chapter 13)

4. Larcum Kendall was a horologist who was tasked with making a replica of the H-4. His replica, entitled the K-1, was deemed an accurate copy, and was selected over Harrison’s sea clock to accompany Captain Cook on his expeditions. (Chapter 13)

5. While not fully appreciated during his lifetime, Harrison posthumously had one of the largest effects on the future of England, as some have determined the invention of the sea clock as the reason for the ease of maritime expansion and, therefore, the dawn of the British Empire. One of the main issues was the cost related to the production of sea clocks, but as more horologists became involved in the “chronometer” production process, prices were reduced and more mariners purchased clocks. (Chapter 14)

6. GMT refers to “Greenwich mean time” or the 0 point of time upon which other time zones are based. Greenwich remained the point of the prime meridian in the century after Maskelyne, and at the International Meridian Conference in 1884, the representatives “[made] the common practice official” of locating the prime meridian in Greenwich, much to the chagrin of the Parisian community. (Chapter 15)