It is difficult to plainly describe Looking for Longitude. Like the early-modern problem of longitude Katy Barrett portrays, precise reckoning is easier said than done. This is a tricky book to peg down because it is not a history of longitude per se, nor is it really a history of either of its main protagonists John Harrison (the clockmaker we most associate with solving longitude) or William Hogarth (celebrated satirist). Barrett tells a story about authors and intellectuals positioning themselves in society, the place (contested and negotiated) of scientific ideas in the public imagination, and how science enriches, enlightens, and elevates public debate far beyond its original context; the book is about how longitude was located within the literary and visual discourses of the eighteenth century. Examinations of the latter are particularly well addressed in the book's 84 images.
Barrett begins Looking for Longitude not with Harrison, as might be expected, but rather with Hogarth and the final engraving in his series “A Rake's Progress” (1735) which depicts a Bedlam inmate diagraming on the cell wall a potential solution to the era's most pressing and stubborn scientific quandary, reckoning longitude at sea. Somewhat surprisingly, Looking for Longitude lacks a clear definition of longitude. The matter is quickly contrasted with the relatively easier task of determining latitude: static horizontal cartographic lines based on the equator versus vertical reference lines, with no fixed starting point, which move continuously beneath your ship as one sails westward or eastward. This is an oversight but one that is understandable given that Barrett's focus is on the cultural location of longitude rather than on longitude itself as a scientific problem. It is a problem that is simple to describe but difficult to solve. Briefly, if you know what time it is at an agreed upon reference point, say, Greenwich, and you know what time it is on your ship through astronomical observation, a comparison of the time at Greenwich with that aboard ship gives you longitude because every four minutes of variance is one degree or sixty miles difference in longitude. But accurate timepieces required to maintain Greenwich time at sea proved an elusive technology. Since Britain's livelihood depended on vessels that knew their precise location at any moment, longitude was a matter of great importance. Parliament established the Board of Longitude in 1714 to evaluate ideas, provide seed money, and award as much as £20,000 for solutions that calculated longitude to a precision of one half of a degree.
Barrett endeavors to show how, like Hogarth's patient who attends to serious computations amidst chaos and the indifference of observers, both Harrison and the question of longitude itself sought to be taken seriously in an age that was more apt to use longitude as satire, the butt of jokes, or more provocatively as a metaphor in sexual commentaries. It was “a cultural key word,” in Barrett's phrase (7). By placing longitude in the hands of a madman, Hogarth characterized those interested in longitude as the lunatic fringe who are foolish enough to attempt to resolve an issue that even Sir Isaac Newton claimed was near impossible. How could Harrison and his contemporaries be taken seriously?
Looking for Longitude is divided into three parts. Part one, “The visual problem,” looks at the maps, charts, and diagrams used to illustrate potential solutions. Part two, “The mental problem,” examines the language and utterances made by innovators and inventers and how their verbal claims of success were “expressed, questioned, and satirized in a wider context” (16). Part three, “The social problem,” considers how could longitude be experienced in polite society.
Given the difficulty of the problem and the richness of the reward, the matter of longitude attracted not only sober mathematicians and skillful horologists but also people of a more dubious reputation. For the interested public who lacked the wherewithal to easily separate a rose of a design from one filled with thorns, all ideas for solving longitude were initially viewed with suspicion. Those who promoted longitude solutions were often labelled as “projectors,” characterized as schemers, scammers, and charlatans. At the time, projecting and mental instability went hand-in-hand, as in Hogarth's print, for example. Therefore, Harrison had to present himself and his chronometers to the Board and to the public in a way that conveyed both his credibility and trustworthiness. Barrett calls these efforts “social self-display” (173).
It should be clear that Looking for Longitude is not really about longitude as a technical problem of navigation. It is not a history of science, nor of mathematics, but a history of how science and its concepts can be incorporated into the collective understanding of a society. This focus means that Barrett offers assertions that may cause a few readers a moment's pause. The claim that we know more about Hogarth's visual satire of longitude than we do about the promoters of solutions to the problem may be true for general readers, but historians of science know otherwise. This is my only criticism of an otherwise excellent book. There was not enough meaningful engagement with previous scholarship on the history of longitude, or on public science in eighteenth-century England. Readers seeking an exhaustive discussion of longitude, or a comprehensive definition of the issue, will have to look elsewhere. To be fair, Barrett never claimed to have written a history of mathematical navigation. Looking for Longitude is about how the public embeds new ideas into itself. In this way the book makes a meaningful contribution to our understanding of how learned knowledge circulated in Augustan England. As much as longitude was meant to determine one's location in the unforgiving waters that framed Britain's empire, Harrison and others had to first determine their location in polite society.
