Found at Sea: Mapping Ships' Locations on the Eighteenth-Century Atlantic Brown Bag Lunch at the Massachusetts Historical Society

I was once again fortunate to be able to attend a brown bag lunch at the Massachusetts Historical Society on June 27. The speaker, John Dixon from Harvard University, shared with us an ongoing project called "Found at Sea: Mapping Ships' Locations on the Eighteenth-Century Atlantic."

In essentials, Dixon was taking ships' logs and translating their information into intricate maps via GIS software. It was a surprisingly original idea, and I was taken with some of the things he'd thought to map and compare.

One of his basic theories was that most of what we know about routes back and forth across the Atlantic in the late eighteenth-century - he was looking at approximately 1775-1800 - comes from idealized sources. Sailors and merchants would publish routes that they believed offered the best advantages in speed and safety, and there were generally agreed-upon trends such as going east in a northerly arc and going west in a southerly arc to take advantage of the clockwise trade winds.

However, until Dixon began mapping, there was really no good way to quantify large quantities of information gathered by actual sailors back and forth across the Atlantic. Did they actually follow those idealized routes? If they deviated, what caused their changes?

Using GIS software allowed Dixon to visually represent those actual routes, and by including data points he could start to see other patterns - for example, in wind, in distance sailed, in weather, and through encounters with other ships - and characterization of those encounters as hostile, friendly, or neutral. Mapping many ships could start to expose patterns in international shipping lanes - one of the best questions from an attendee was whether Dixon belied his work would provide a new way to talk about conceptions of national boundaries at sea. Was there a clear sense of national identity among merchants and sailors, or were there occasions in which a maritime identity trumped that nationalistic sense? (He thought it would, but wasn't far enough along to offer any theses of his own.)

One thing I learned and was glad to think about was how fluid the ideas of communication and location were while at sea. For one thing, while latitude was fairly easy to make, no one had yet come up with a simple and easy way to mark longitude. Ships could be much further east or west than they thought, and would often hail other ships to compare longitude in order to get a fix.

For another, sometimes it was difficult to discern the nature of an encounter at sea. Sometimes French warships chased French merchant ships and only realized their mistake when they caught up; sometimes ships chased one another without ever knowing the identity of another ship; sometimes there were genuinely hostile or friendly encounters that lasted for days. Thus, even what ultimately was a friendly encounter could have all the characteristics of a hostile encounter.

I love projects that do what Dixon did: harness the power of technology to expose new and interesting ideas about history. Maritime history can particularly benefit from GIS systems. I was intrigued to think about how I could apply some of these same ideas to my own work - the catch, unfortunately, is that cavalry officers rarely, if ever, recorded their latitude and longitude with the same precision as sea captains.