Contributed by Lynn Nelson and produced by Susan Stafford.

     The Surveyor's Trade, by Lynn H. Nelson

Lynn Nelson, professor of history at the University of Kansas, formed a company and continued to survey during the summers all through his graduate school career. This pursuit included reconstructing original surveys from the field notes in order to try to find the reason for discrepancies between one old survey and another or to suggest where a lost original marker might be found (the Texas Supreme Court once accepted one of his reconstructions as "an expert opinion").

So when Lynn was asked about prime meridians and longitude, he had the answers ready to hand (and nothing is quite so good as an answer from Lynn Nelson!). We are very grateful for permission to share those answers with you.

Q. How or why was the 6th Principal Meridian set 108 miles west of the Missouri River? The longitude is not a special one, being 97 degrees and some odd minutes West.

     The basic answer to this question is that a meridian is simply a line running directly between the north and south poles, and its longitude is determined by the time at which the sun passes over it. The base is taken from the Royal Observatory at Greenwich, and the meridians are numbered westward from that point. Since the sun sweeps fifteen degrees of arc each hour (360/24=15), the meridian at eight hours Greenwich lies at a longitude of 120 degrees. Since these measurements depend upon the accuracy with which can measure the time difference between Greenwich and a given point, lines of longitude were not fixed with any great degree of precision until well into the nineteenth century.

     From a surveyor's point of view, however, one can set a meridian wherever one wishes, and set further meridians at any angular distance from that base that suits ones purposes. The angular distance between meridians decreases as one moves north, however, so the surveyor has to be careful to measure along a given parallel, or degree of latitude (angular distance from the equator). This is rather easy, though, since one can check one's latitude by measuring the elevation of the sun or some other celestial body at a given time.

     The First Prime Meridian and the degrees between it and succeeding meridians were set by the Northwest Ordinance, and all succeeding federal surveys have been based on those original specifications.

     Why 108 miles between the two surveying monuments? Well, a surveyor can operate using standard geometry for nine miles. Beyond that distance, the curvature of the Earth becomes a factor, and the surveyor has to switch his calculations of lines to spherical geometry and his computation of angles to spherical trigonometry. Besides, after chaining nine miles, one is liable to have wandered off-line and it is well to check one's parallel. So a surveyor setting a long line will (or rather, should) stop each nine miles to check the parallel by an astronomical observation. (At least they used to do so. Now, they simply take a reading from a satellite.) The surveyor then establishes an intermediary point and begins over to survey the next nine miles using plane geometry and trigonometry.

     In any event, back in the 1850's, 108 miles was a good distance between markers, since it was evenly divisible by nine (108/9=12). When aiming for a principle meridian, the surveyor would usually start with an astronomical reading on some part of the parallel that had already been established, at some distance divisible by nine from the point he wished to reach.

     The error of 2.2 miles south of the parallel in 108 miles of chaining is quite interesting. It amounts to an error of two percent, which is really quite extraordinary. Surveying errors on a long line normally tend to cancel each other out, with a drift to the north on one leg being balanced by a drift to the south on the next leg. It had to be a cumulative error in his astronomical readings, and I would guess that his watch was running slow (and so making the elevations he was measuring seem high). I hope that he got it checked before his next job. Those old chronometers are wonderful pieces of work, but they need to be treated with a great deal of care. If you ever get your hands on an old surveying chronometer, treasure it as the finest example of the watchmaker's art.

Q. How is something like surveying thought of? Where do these ideas come from?

     I should explain that I took up land surveying and civil engineering after a stint in the Army during the Korean Police Action (No, it wasn't a war. They kept telling us that.) I was twenty-three at the time and knew nothing but making steel, warehousing, and going to school, and it seemed to me like a good idea to learn a profession before returning to graduate school and seeing whether I had what it took to earn a PhD. I went to work for a seventy-year old surveyor in Amarillo, TX. I worked and he taught until I finally stood and passed the examinations for Licensed State Land Surveyor and Public Engineer. After a while, I returned to graduate work and finished a doctorate in Medieval History. I've been very happy with research and teaching, but I also look back on my days as a surveyor with a good deal of pleasure. Carolyn wants to know, I think, how the techniques of such a profession develop, and why people are willing, no, happy to spend their lives doing such things. The first is worth a book, and, in fact, several books have been written on the subject. I suppose, though, that the matter of the pleasure to be drawn from such work is an individual thing, so I'll try to explain something about what gave me pleasure.

     I think that a good deal of it had to do with simply working outside most of the time. My teacher/boss operated on the principle that the more one knew, the better off one was, so I learned the history of the lands we surveyed -- in fact, an anecdotal history of the Texas Panhandle. So the lands we worked on were populated by Col. Goodknight, the XIT hands, Charlie Hayden, the folks buried at Old Tascosa, and a lot of other things. He also believed that one should pay attention to the land, so I was able to see things that other people were not aware of, the gentle drifts that mark old fence lines, the little chips of flint that tell you that somewhere nearby an indian had once set up shop to make some arrowheads, the odd rosebush growing of the south side of some little hill that marks where someone's kitchen door once stood. When you work outside, you learn the weather, and when you work in the Texas Panhandle, you learn to smell water. One has to be careful, so you learn to look down when you step down onto the sunny side of a rock in the morning or evening, and on the shady side during the height of the day. You learn that, if you unexpectly blunder into a skunk, you can get by if you're only polite and say good morning, or good afternoon, whichever the case may be. You learn to sit in the sun when the mosquitoes rise in the cool of the evening, and not to look for the little bird chirping somewhere unless you have some use for a bull snake. Learning to understand the language of dogs is a study in itself, and one that you master if you want to avoid rabies shots. You also become aware of all of the wildlife that finds whatever you're doing so fascinating that they simply have to follow you and watch. If you learn from someone like Howard Trigg, the job is one that will take three or four days to complete, and you're camping for the night, you sit for a long while and learn to recognize the stars and planets, watching them rise up and sink down. Like as not, you'll be joined by an old rancher, railway man, or someone else with a sackful of reminiscenses and experience that you can't buy with money.

     In amongst all of this, you're constructing an exact geometric figure, keeping notes of how you're doing it, planning ways of balancing errors, and transforming a bunch of lines on a sheet of paper into a dam and lake, a highway, a factory, a new subdivision or even a town, or re-running a line that that was surveyed a generation ago and retracing the steps of your predecessor, checking his figures and trying to find the marks he left to guide you. In doing so, you look for signs of how the land has changed since he made his way through those parts, and how it's likely to change before the next fellow comes through so that you can leave your markers someplace where he'll be likely to be able to find them. All the time, you're picking up stories such as that of the rancher who was told by the surveyor to take good care of the cedar stakes that had been driven into the section corners of his land. When the rancher died, and the time had come to resurvey his land for the estate executor, the survey markers were found in a safe deposit box in the First National Bank of Amarillo, where the fellow had put them in 1920.

     I never needed background music and wouldn't tolerate anyone who thought they had to have earplugs in their ears while they worked. People who did so had no feeling for the land through which we were working our way. I generally convinced them of the validity of my point of view by showing them the knife blade that I would use on them if they got themselves bit by a rattlesnake. There are people who save up their money and vacation time so that they can take long hikes along historic trails, observing the fauna and flora, stopping at special sites, reading brochures, and generally getting acquainted with nature. Surveyors spend their lives doing pretty much the same thing.

     Finally, I must confess that I enjoyed the respect that I was shown. You see, people have to be able to trust surveyors. An oilman thinks that he knows where some oil is to be found and decides to drill a well there. First, however, he has to get the lease, and hire a surveyor to locate the lease and stake the site where the well is to be drilled. Such information is, as you might guess, worth a great deal of money. I never heard of a Texas surveyor who betrayed his trust in this or similar matters, and neither had anyone else in the Panhandle. So they regarded a professional surveyor as a person of absolute integrity and honesty. It gave me a great deal of satisfaction to try to live up to such a standard to the same degree that my predecessors had and my fellows did.

     I suppose that I would sum it up by saying that, when surveying, I was more aware of my surroundings -- extending all the way out to the stars on which I would take my readings (Fomalhaut being my favorite) -- and more alive than most other ways of life demand or even permit.

     That's not a real answer, Carolyn, and, after having tried to answer you, I don't believe that I can.

Q. Wait -- "not to look for the little bird chirping somewhere unless you have some use for a bull snake" -- what do you mean?

     The only reason that Larry was on my survey crew was that his father was a friend of the owner of the company to whom I had contracted myself and my crew for the summer of 1956. Larry had been a goof-off as a boy and, in three years in the Air Force, he had become a man but was still a goof-off. His father thought that a summer out-of-doors doing some honest work would do him some good, and I had been persuaded to accept him in exchange for re-negotiating my contract at a level that would cover Larry's salary and leave a good deal left over. I came to regret that decision, but, at the time, I was interested in building up the capital reserve that I intended to distribute when my crew graduated college and I would dissolve my company.

     I tried Larry at every position on the crew, but he seemed to think first, that he knew everything there was to be known; second, that being from New York made him infinitely more sophisticated than his associates; and lastly, that we all shared his attitude that a job was a state of affairs in which one tried to enjoy oneself as much as possible without getting fired. As a chainman, he lost pins, as a rodman, he never watched the instrument man to read his hand signals, as a recorder, his attention was always distracted when the instrument man read out angles or levels, and he wrote in such a manner that, after ten minutes, even he could no longer tell the difference between a 1 and a 7. I finally gave him a machete (which he used every device to avoid sharpening) and set him to the task of clearing our lines -- with perhaps a secret hope that he would manage to injure himself so badly that his father would want him to return to New York. Even here, he was a failure. He lacked any sense of the land under his feet and would usually stray down even the gentlest slope, leaving the chainmen to make their way through shrubs and thorn bushes, trying as best they could to snake their chain under the growth. Needless to say, he was not well liked, especially since he was forever taking a smoke break and striking up a conversation, usually about the women he had known, with one of the crew who was trying to get something done.

     One day, while we were surveying some open and windswept sections that had once been part of the great Matador Ranch, I set Larry to the task of clearing tumbleweeds out of the way of the chainmen. The steady winds in that area came from the northwest, so the tumbleweeds were piled head-high and yards deep where the fences met at the southeast corners of the sections. Larry didn't like this work, particularly since the head chainman was usually right behind him, waiting impatiently for him to clear a path. As Larry was reluctantly and grumblingly engaged in this task, there was a small chirping sound from somewhere among the tumbleweeds. No bird in its right mind would build a nest in such a place since, during shedding, rattlers, who are blind when shedding their old skins, will drift downwind into exactly such places. So the chirping was obviously from a bull snake, who -- being rather fat and lazy -- try to entice small predators to come looking for the birdie.

     My head chainman, though, went on about how the chirping sounded like a young paisano (roadrunner); how, if one could catch a young one, one could raise it as a pet; and how he had a friend who did that and eventually sold it to a rare pet dealer in New York for five hundred dollars (about $2500 in today's money). Larry soon decided to take a smoke break, and went in search of a valuable young paisano, crawling carefully on his hands and knees, and feeling his way through the tumbleweeds.

     I wasn't paying much attention at the time. Our work had stalled because of Larry's grudging pace, and Charley, an Assinaboine who was my front rodman, and I were looking for a good rattlesnake. The head of the company had promised an out-of-state client a fine rattlesnake belt and had asked me to get him a snake for the belt-maker. We had found one, and Charley had dispatched him by grabbing his tail and giving him one sharp underhand snap. We had then taken the rattler to our jeep and coiled him up safe and sound in our box of spare chains. It was about then that we heard a series of piercing screams and saw Larry, running faster toward the jeep faster than I would ever have believed him capable of moving. His face was dead white as he drew near, in spite of his having run a quarter of a mile at top speed, his eyes were rolled back and white like those of a spooked horse, and he was wildly hacking at the air in front of him with his machete. Charley and I started forward to take him down, but thought better of it. Larry headed straight for the jeep and, once there, starting throwing things about, desperately hunting for something.

     Now it had never occurred to me that anyone would have tried to sneak a bottle of whiskey onto the job. Any one of us would have smelled it as soon as the bottle was opened, but Larry hadn't seemed to have been aware of that. Unfortunately for all concerned, he had chosen to hide his rye (Charley said it was typical of Larry to drink rye whiskey, since the best rye ever made was not as good as the worst bourbon) in the chain box, under our spare chains. Larry needed a drink and needed it badly, found the chain box, tore open the lid and dove in to find his bottle. What he found first, of course, was a rather large rattlesnake, and he began to scream again. He started hacking away at the rattler with his machete, and kept hacking until he sank to the ground, pretty well exhausted.

     We decided to wrap up for the day and take Larry back to Amarillo to get him some of those new-fangled Milltown things. We also took back a smashed chain box, a large number of bits of rattlesnake, four chains -- including an old and treasured 100-vara job -- cut, bent, and twisted so badly that it was difficult to separate one from the others, numerous shards of glass, and a strong smell of cheap rye whiskey.

     We never saw Larry again and supposed that he had headed back to a New York where the only reptiles one need fear are the giant alligators that infest the sewers. Life settled back into a more even course and we soon caught up with the work in which we had fallen behind because of Larry's inability to pay attention to things. I had thought of talking to Froggie, my front chainman, about how dangerous and disruptive his little joke had been. I gave that up the next morning when we learned that Larry would no longer be with us, and the president of the company and I agreed that our contract would continue to include his salary even if he would not be around to collect it. Froggie could only see the bright and sunny side of the whole affair, remarking that, as usual, Larry had gotten things backwards -- that one is supposed to find one's bottle first, and only then start to see snakes.

Q. When reading Longitude by Dava Sobel, I was wondering, how do you even think or consider solving or even realize there is such a thing as longitude? How does something like an invisible line get solved?

     People have known that the Earth was a sphere for a long time (you can forget that stuff about medieval Europeans thinking that it was flat) and have even known its approximate size since the 200's B.C.. It was a sphere, and the only way to establish locations on its surface was to set up two sets of lines that would intersect each other at regular intervals and as close to right angles as possible. The ancient Greeks has figured that out, but then they had Euclid and Eratosthenes.

     It was easy enough to determine how far one was up and down on the surface of the Earth because the stars and planets, suns and moon, all revolve (or appear to revolve) around a common center located directly above the North Pole, and there is a star (Polaris) close enough to that point as to make no difference at all, given the accuracy of the measuring instruments of the day. So Polaris lay exactly on the horizon at the Equator (zero degrees elevation above the horizon) and directly overhead at the North Pole (ninety degrees elevation). So one could find one's latitude simply by measuring the angular distance from the horizon to Polaris and subtracting that from ninety.

     Establishing another set of lines that would intersect the first was a bit more difficult. Since they knew the approximate distance around the Earth, they could establish the distance around at each degree of latitude (the distance gets shorter the farther north one goes). If they could set markers accurately all the way around the Earth on a single line of latitude, they could construct other markers where a degree of longitude intersected a different degree of latitude. So Greeks, Romans, Persians, and others industriously measured East-West distances and, by using their starting points as zero degrees of longitude, managed to make an approximation of a base meridian and calculate the location of places in Europe and the Near East on that basis.

     It wasn't too satisfactory, however, even after Marco Polo travelled from the Crimea to the Yellow Sea, recording how far each place was from his starting point. Overland travel wandered all over the place and provided only a crude approximation of a scheme of longitude and latitude, but it was one that worked well enough at the time for the Europeans. But if overland measurements of distance were crude, measurements by ship were worse. When Columbus discovered the New World (He thought it was Japan or the Indies because he thought that the Earth was considerably smaller than it is and than everyone else supposed it to be), the Europeans soon got quite interested in knowing exactly how far further China was. That meant that they had to find some way of measuring longitude across great distances without depending on crude measurements.

     There was a way, but, to be able to use it, you needed to know something close to the exact time back home. You see the sun revolves around the Earth every twenty-four hours, so if you knew that noon back home was at twelve o'clock and your timepiece, which you had kept running at the time back home, showed that the sun was overhead at three o'clock in the afternoon, you knew that the sun had travelled three hours to reach you, and so has travelled one-eighth of the way around the world (24 hours/3 hours=8). Since it travels fifteen degrees each hour (360 degrees/24 hours=15 degrees), you knew that you are 45 degrees West longitude.

     But you need a very accurate timepiece to measure longitude in such a fashion. If your clock ran fast or slow by as much of a tenth of a second a day, you couldn't even guess where you were after three or four weeks out of port. So the centuries since then have witnessed continual efforts to make increasingly accurate chronometers. The ones they use today are periodically and automatically reset by a satellite impulse generated from the atomic clock the National Bureau of Standards. But they weren't accurate enough by the beginning of the nineteenth century for the framers of the Northwest Ordinance to try to fit the meridians by which the public lands were to be surveyed into any global scheme. So they established the First Prime Meridian at a convenient location on the line of forty degrees north latitude, and began to chain the proper distance to reach the second meridian, using their own chronometers, set to the time of the First Prime Meridian to check the accuracy of their lines.

     In answer to the question of why people ever thought of such a thing as longitude, the answer is that you need two intersecting sets of lines to locate things in the world. They had latitude and developed longitude because they desperately needed the other set of lines if discovery and exploration, and settlement, were to be possible.

     Q. Can you explain to me how they were able to know the measurement of the earth? How would knowing about the stars and their placements at different times in the sky give them the size of the earth? Or is this calculated in the 24-hour time frame? Then timewise they would know how far, but milewise? Though others might not be interested in this . . .

     How could anyone not be interested in hearing about Eratosthenes' calculation of the circumference of the Earth?

     First of all, people who had thought about the matter had known for some time that the Earth was a sphere. There were two basic demonstrations of this. First, no matter where one is (provided the surface is level) and no matter in what direction one looks, one gradually loses sight of things (like a ship) that are moving away from one, and that loss progresses from the bottom up. In addition, the ratio between the amount of the object that one loses sight of and the distance the object is from one is the same no matter where one is (seven feet per mile). This means that the Earth's surface is equally curved in every direction from every place, and the only solid object with a surface of which this is true is a sphere.

     Second, they believed that both the sun and moon revolved around the Earth, and so knew that an eclipse of the moon took place whenever the sun and moon were on opposite sides of the Earth at night. So they understood that the shadow that crept across the moon was that of the Earth. Now, wherever one was when an eclipse occurred, one could see that both the leading edge and the trailing edge of the Earth's shadow formed half-circles. Again, the only object that casts a shadow in the shape of a circle no matter how it is oriented is a sphere.

     The Earth isn't a perfect sphere, of course, but they believed it was because they believed that the shape all celestial bodies (of which they considered the Earth to be one) was perfect.

     Eratostenes, who died about 194 B.C., was a scholar in the Museum (a sort of research institute attached to the greatest library of antiquity) who figured out a way to measure the circumference of the Earth. In an oasis some distance south of Alexandria, there was a very deep well, so deep that the sunlight reached to the bottom only at high noon one day each year. Eratosthenes assumed that the sun was a great distance away, so far that its rays fell on the Earth as parallel lines. (He had justification for this, but that's another matter.) If so, then the sun would be directly overhead at high noon on a given day on only one parallel of latitude. South of that parallel, the sun would appear to be north of one, and north of that line, the sun would seem to be south. Furthermore, since the well was absolutely straight as measured with a weight on the end of a long string lowered to the bottom of the well, the sun's rays that reached its bottom must be perpendicular to the Earth at that point and time.

     So Eratosthenes set up a tall pole at Alexandria and made sure that it was as vertical as possible. When high noon came and the sun's rays were striking the bottom of the well to the south, the pole cast a shadow to the north, Eratostenes measured it and so could construct a triangle. The angle from the top of the pole to the end of its shadow could be calculated from the height of the pole and the length of the shadow. If the shadow and pole were of the same length, the angle would be forty-five degrees, If the pole were twice the length of its shadow, the angle would be twenty-two and a half degrees, and so on.

     If you figure that both the pole and the well are pointing to the center of the Earth, and the sun's rays are falling everywhere as parallel lines, then the angle between the top of the pole and the end of its shadow is equal to the angle between the well and the pole if the lines of each were drawn to the center of the Earth. So he now knew how many degrees of latitude south of Alexandria the well was located. He also knew the distance, since it had been measured very carefully for this project. He then divided the degrees of latitude between Alexandria and the well into 360 degrees, and multiplied that number by the distance between Alexandria and the well.

     Lo, and behold! He had the circumference of the Earth. Of course, his equipment was a bit crude and his distances were not absolutely accurate, so he was off about two percent. A chap by the name of Claudius Ptolemy came along later and made some corrections and, naturally, made it wrong by about ten percent.

     I hope that you could follow that. It's easy enough to describe when you can lay it out on the blackboard, but a bit difficult using only words. At any rate, I think that it is probably the most elegant experiment in the history of science. It used a minimum of equipment and only two assumptions, and it proved exactly what Eratosthenes had set out to prove. The oil drop determination of the charge of an electron may run it a close second, but I don't believe tops it.

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