POBasked about his book, Drawing the Line,How Mason and Dixon Surveyed the Most Famous Border in America.

Imagine starting out on a survey job to settle a boundary dispute…and completing the job by drawing a line between free and slave states. Charles Mason and Jeremiah Dixon, two English astronomers, did just this beginning in 1763, commissioned to end the feud between the Baltimore family of Maryland and the Penn family of Pennsylvania.

Mason and Dixon ended their adventurous undertaking of 325 miles after five years, completing the first geodetic survey, measuring the first degree of latitude and taking the first scientific gravity measurements ever recorded in America.

In his book, Drawing the Line, How Mason and Dixon Surveyed the Most Famous Border in America, English surveyor Edwin Danson unveils the intricacies of their trek and highlights the many successes in the surveying field. What follows is an exchange with Danson and POB’s columnist, Milton Denny, PLS.

Denny: When and how did you first become interested in the Mason and Dixon Line?

Danson: Sometime during the late 1970s I was chatting with a friend, Geoff Thornton, and he told me something of the work of Mason and Dixon. I recall being intrigued but didn’t think any more of it until about 1990 when I started to visit the [United] States on a regular basis.

Denny: What led you to learn more about the mechanics of laying out the Line?

Danson: The topic came up one evening in Houston. None of my American colleagues knew much about the Mason-Dixon [Line], so I decided to find out more. At the time I don’t recall thinking, “Well, this is an amazing bit of surveying,” but as soon as it became apparent that there was hardly any information to be found from the usual sources, it got me thinking, “How would they have done it?” I asked myself how I would have done it! My first real break came from browsing in a secondhand bookstore in New Orleans when I discovered a 1950s colorful rendition of America’s frontier history.

Denny: How well-known is the work of Mason and Dixon in England?

Danson: I’m sad to say hardly at all. But hopefully that’s been partially rectified by the publication of the book. Certainly many people have heard of the Mason-Dixon Line, but few know what it really is. As for the other work of Mason and Dixon, very little is known, which in my mind is a real pity as they were both British and, in their day, well-known and respected.

Denny: I think most surveyors know the story about why the line was surveyed. Is there anything you learned in your research for your book that surprised you about the Line?

Danson: The short answer is just about everything! Everything about the work was fresh and exciting. To understand exactly what they did and how they did it, I went through Mason’s journal reconstructing each day’s work in my mind. Luckily, I had some experiences from which I could draw a parallel. I immersed myself in the historical context as best I could, which when it really comes to understanding the Mason and Dixon partnership, is obligatory. Their extraordinary attention to detail in the most challenging of circumstances was the most surprising. For me, and I have yet to find anything to the contrary, the merger of the skills, methods, knowledge and characters of these two men and their American colleagues symbolizes the birth of geodetic field surveying. Up to that time, no one had actually conducted a full-scale “geodetic” survey employing such a definite mix of astronomy and higher land surveying; that is to say without at some point resorting to a compass. Apart from the French meridian arcs, triangulation for mapping control such as Cassini’s map, was in its infancy. Mason and Dixon et al broke the mold and the techniques they pioneered became the foundation for the great surveys that followed.

Denny: How long did it take you to research and write your book?

Danson:Drawing the Lineis of course about the Mason-Dixon Line, but it also examines the background to the boundary dispute and the events that led to Mason and Dixon’s appointment. The men’s background and careers are also covered as are their adventures in South Africa. By way of introducing average surveyors to the nuances of astronomy and surveying, the book perambulates through the development of Earth measuring and the relevant work of the French. So, there is a lot more in the book than just the Line. Over four or five years I accumulated information from around the world and unraveled the various leads I discovered. Piece by piece I assembled the information in chronological order, my plan being to write a paper. I did, in fact, write a paper but it was too long for a magazine article and too short for anything else. A book-sized work was the only alternative.

My wife (an English teacher) asked me a simple question: what were the really important issues? It was then that we lighted on the idea of a popular history, something that would do justice to the two men but not be too technical that it would put ordinary readers off. Only then, in about 1995, did the real work begin and the project turned into something of an obsession. The toughest part came once I had a publisher clamoring for copy! It took nearly a year working with the editors at John Wiley to fill in the gaps and turn the manuscript into a book. I started at 5:30 each morning and completed a section before going off to work.

Denny: What lessons did you learn as a geodesist from studying the procedures for surveying the Line?

Danson: Mason adopted what, for the time, was an unusual expedient—he reduced all his latitude observations to the starting latitude at the Post mark’d West; in effect this was his datum point and this procedure reveals a very astute mind at work. I also noted how they reacted to the commercial pressure to get the work done quicker, which they solved by alternating latitudinal observations with an offset change of direction. It wasn’t until I worked out one of these for myself that I realized what a clever stroke of brilliance that was!

Their degree of latitude was an education. Until learning about this, I didn’t have a lot of knowledge and had to go back to some early works. As far as I am aware, no one had ever measured a 100-mile long line over the ground using measuring rods and chains. The French used triangulation. The Mason-Dixon crew invented the techniques as they went along and you can see from the journal how this developed. In retrospect they could have done better, but in their defense there was no precedent for them to follow. Maskelyne, Roy, Lambton and other great geodesists that followed turned baseline measurement into both an art and science, but it was Mason and Dixon who showed it could be done.

Denny: What future research do you have planned on the Mason and Dixon Line?

Danson: Since the book came out, I have heard from many people and met many others who share a passion for the Line. There are so many practical questions unanswered; I think the only way to resolve them would be to build replica instruments and actually conduct an 18th century geodetic survey. At one point it looked as though there might have been a documentary film on the Line but in the end the backers didn’t think it would get the necessary ratings. I still think it would make a great movie—Mel Gibson as Mason and Bruce Willis as Dixon! Perhaps Burt Reynolds could play the learned Governor Sharpe!

Denny: Are you engaged in other research related to surveying? Are you writing any other books?

Not being a “gentleman of independent means,” I have to eke out a living as best I can so time for research is limited. As for another book, yes, I am well on the way with another tome. In its way, it is both a prequel and a sequel to Mason and Dixon and looks at the development of the science that came to underpin mapmaking.

Like Drawing the Line, it is set within the context of the socio-political history and exploration of the 18th century. It is “popular history” again; to my mind the most important sort of history because it opens up to ordinary people fascinating worlds that would otherwise be hidden away on university library shelves. I enjoy unraveling the science and surrounding it with real-world events that put the developments in context; it makes reading more lively and adds texture to what can so easily be a riveting dull subject.

Edwin Danson, MRICS, FInstCES, is a geodetic surveyor with 35 years of experience. He is a Chartered Surveyor of the Royal Institution of Chartered Surveyors and a Fellow of the Institution of Civil Engineering Surveyors.

Order Drawing the Line on the POB Online Store at www.pobonline.com/books. Click on History & Biography.