Boundaries

by Sally M. Walker

  This page from Mason’s journal records the stars he observed from December 30, 1763, through January 2, 1764, and their positions in the sky.

  Unfortunately, the good news of the sector’s success was tempered by upsetting news as more information concerning the Conestoga Indians filtered into Philadelphia. Young Christie, awakened by gunshots and screams, had escaped from his house. He had run to the home of Captain Thomas McKee and told him what had happened — including the fact that thirteen Conestogas had been away from home at the time. Christie didn’t know what had happened to those still at home.

  According to rumors, the Paxton Boys still intended to kill Will Sock, who was not among the dead. Fearing for the remaining Conestogas’ safety, local magistrate Edward Shippen placed them into protective custody. By December 17, fourteen Conestogas — four men, three women, three little girls, and four young boys, including Christie — sheltered inside Lancaster’s new brick workhouse, guarded by the sheriff. Express riders galloped messages between township and provincial authorities. Officials requested that anyone with information about the perpetrators of the crime step forward. John Penn, the governor of Pennsylvania and a grandson of William Penn, issued a proclamation for the capture of the men who had “inhumanly killed six of the Indians.”

  After the Paxton Boys’ December 27 massacre of the Conestogas in Lancaster, their mob grew. Nearly 250 men, angered by Indian attacks on the colonial frontier, reached the outskirts of Philadelphia. Benjamin Franklin and other community leaders persuaded them not to storm the city.

  Meanwhile, the Paxton Boys readied themselves for another attack. At midafternoon on December 27, between eighty and one hundred men carrying “Muskets, Tomahawks, & Scalping knives” rode into Lancaster. They dismounted and walked to the workhouse. Threatened by the armed mob, Sheriff John Hay and the coroner, Matthias Slough, stepped aside. The Paxton Boys broke in the workhouse door and, in a manner even more brutal than the first attack, massacred the unarmed Conestogas inside. No one escaped. After less than twelve minutes, the Paxton Boys left the workhouse, mounted their horses, and rode out of town. None of them was ever caught.

  The news of the Lancaster murders further horrified Mason and Dixon. But they still needed to continue their work. By the end of the first week of January 1764, the surveyors had finally finished stargazing. Mason completed his calculations. (Without calculators or computers, several days of mathematical computation always followed long periods of observing the stars.) After two days, he informed the commissioners that the latitude of the southernmost point of Philadelphia was 39 degrees 56 minutes 29.1 seconds north (39°56′29.1″ N).

  With one preliminary task accomplished, the surveyors moved on to the second: surveying to a point fifteen miles south of their current location — which would be the latitude for the West Line, the long boundary line that ran east to west between the provinces. However, traveling directly south fifteen miles and then turning west would have required surveying across the wide Delaware River twice. Mason and Dixon avoided the unnecessary inconvenience by first riding thirty miles west of the southernmost point of Philadelphia to a location where they could survey southward far from the course of the Delaware River.

  Richard Peters, one of Pennsylvania’s boundary commissioners, had assisted the survey crew in running a temporary boundary line in 1739. Peters knew that wilderness travel was arduous. Before Mason and Dixon left town, he sent them a friendly letter that began, “Gentleman: I hope you have pleased yourselves with good horses and an agreeable companion.” Their companion may have been Joel Baily, a clockmaker and gunsmith, who lived three miles from the surveyors’ destination. An experienced surveyor, Baily was also interested in astronomy. He accompanied them to John Harlan’s home, at the fork of Brandywine Creek. Harlan, a Quaker, agreed to board the surveyors and also told them they could erect their wooden observatory in his garden. In the years that followed, Harlan’s sturdy stone house would become Mason and Dixon’s American home. They would come to know Harlan’s wife, Sarah, and their five children as if they were family.

  John Harlan’s stone house, at the fork of Brandywine Creek, became Mason and Dixon’s home away from home while they were in America.

  For now, Mason and Dixon returned to Philadelphia and prepared to move west. Two carpenters dismantled the observatory and “put [it] with the rest of our Instruments into the wagons.” The surveyors feared that a bone-rattling two-day wagon ride would damage the zenith sector, so rather than loading it with the other instruments, it was wrapped, boxed, and then “carried on the Springs (with Feather bed under it) of a single Horse chair [carriage].” Both carpenters accompanied the surveyors back to Harlan’s house.

  Eager to begin, Mason and Dixon set up the zenith sector inside a tent in the garden. They used the stars Capella and Beta Aurigae to confirm their location. The zenith sector’s measurements pleased Mason: “Finding we were very near the Parallel [of latitude] of the southernmost point of Philadelphia, we ordered Carpenters to Erect the Observatory.”

  The surveyors sent regular dispatches to the boundary commissioners to report their progress. At the end of January, Mason wrote to Commissioner Peters,

  I’ve here the pleasure to acquaint you that all our Instruments came here without receiving the least damage. By the few observations we have made, our situation is not far from the Parallel requir’d. As soon as we have settled the south end of the 15 miles, we shall not fail to acquaint you of it. A great number of Labourers will then be wanted.

  Occasionally, Mason interjected a personal request. Thinking of letters from his family that might arrive in Philadelphia during his absence, he noted to Peters:

  When I left Philadelphia I desired the Post Master to deliver my Letters (if any should come from England) to you, a freedom I humbly beg you will pardon, and be pleas’d to keep them ’till opportunity serve to send them to hand and the favour will always be acknowledg’d.

  During January and February, Mason and Dixon came to know John Harlan’s yard well. But working in the garden was no picnic. They slogged through slush after mid-January snows. They shivered until the observatory’s broken stove was mended. And even afterward, being in the observatory was still colder than sitting by the large fireplace in the Harlans’ home. At the end of a long night’s work, they were glad to climb the steep stairs up to their beds in the warm house.

  By the end of February, Mason and Dixon had determined that the latitude of the observatory in Harlan’s garden was 39°56′18.9″ north. This was 10.5 seconds of latitude farther south than the southernmost point of Philadelphia. Mason noted the difference in his journal. He would account for this difference mathematically later, when he and Dixon were fifteen miles farther south and determining the actual latitude of the West Line. Finally, with the latitude of Harlan’s garden established, they began their second preliminary task: measuring to the parallel of latitude that was fifteen miles south.

  Nearly two weeks of gray skies, snow, and rain delayed them, leaving everyone as gloomy and cold as the weather. One evening, during a short break in the “flying clouds,” Mason observed the polestar, also known as the North Star or Polaris, just as it crossed the meridian directly above him. Mason realized that physically marking the meridian’s location on the ground would be a daytime anchor for Dixon’s instrument and make his surveying work easier. To mark the meridian’s location, the surveyors turned a large, oblong rock on end and settled it in the soil — a digging job that was likely assigned to the considerably younger backs of the Harlans’ oldest sons, Phinehas and Jesse.

  But cloudy skies during his observation of the polestar left Mason questioning the accuracy of the rock’s placement. A week later, under clear skies, Mason observed the polestar again and had his crew reposition the rock to mark the meridian more accurately. Dixon often used the rock as a benchmark when surveying and measuring distances from the observatory. It wasn’t long before the Harlans and their neighbors started calling
the large rock the Stargazer’s Stone.

  The Stargazer’s Stone, placed in the Harlans’ yard, anchored Mason and Dixon to the meridian.

  On Sunday, March 17, the night sky offered a special treat: a lunar eclipse. Though Mason had seen many eclipses, the spectacular event impressed him: “The edge of the Sun’s Shadow on the Moons disk was the best defined I ever saw.” Afterward, clear skies and clear weather allowed the survey party to begin its fifteen-mile trek south.

  CHARLES MASON, with his expertise in astronomy and mathematics, directed the duo’s work during the early weeks of the boundary-line mission. Dixon’s expertise as a surveyor took center stage as the focus shifted from the stars to the ground. But before Dixon could begin his work, he needed a vista — a clear line of sight — along the meridian he planned to follow south. Within forty-eight hours of the lunar eclipse, four axmen, wood chips flying, steadily cut a “visto in the Meridian Southward.”

  Surveying across the land required using different instruments from those Mason had used so far. The zenith sector, perfect for measuring angles on the celestial sphere, couldn’t sight or measure land distances. Instead, Dixon used a circumferentor, an instrument that looks like a large compass with built-in leveling bubbles and two upright bars used to sight distant objects. A circumferentor indicates direction (north, south, east, and west) and can measure horizontal angles that are necessary for accurate land surveys. The land survey also required the addition of a few new crew members, all with previous surveying experience.

  Dixon used this circumferentor to keep the chain crew on course as they surveyed south from Harlan’s garden. The instrument in the middle is a compass, and the two liquid-filled tubes are levels.

  In Harlan’s garden, outside the observatory, Dixon aligned his circumferentor with the meridian. A crewman stood several hundred feet away, holding a wooden stake. Dixon peered through the instrument’s sighting slits (one on each upright bar) and signaled the crewman to move right or left until the stake was aligned with the instrument’s sights. Aligning the crewman with the two sights ensured a straight line. After setting the stake in place, it was time to haul out the chain — a two-man job.

  Under Dixon’s direction, two chain carriers measured a distance from the circumferentor with a surveyor’s tool called a Gunter’s chain. This sixty-six-foot-long metal chain consists of one hundred links, each of which is 7.92 inches long. A link of a Gunter’s chain is formed from a straight metal bar. Each end of the bar is bent to form a small circle. Small measured metal circles connect the links. Eighty chains equal one mile (5,280 feet). One chain carrier firmly anchored the end of the chain at the starting point outside the observatory. The other chain carrier unfolded the chain as he walked toward the distant wooden stake. When the chain was completely extended, he stopped walking and stretched the chain taut. On the ground, he marked the spot beneath the end of the chain with an iron pin. This completed one chain.

  A Gunter’s chain was the chain bearers’ constant companion. From time to time, the circles connecting the links became stretched out and had to be reshaped to keep the length of the chain accurate.

  Keeping a tally, Dixon and the chain carriers repeated these steps until they reached the distant wooden stake or a land feature that created an obstacle, such as a creek. At 9 chains and 61 links (634 feet 3.12 inches) from Harlan’s garden, the crew reached the sloped bank of Brandywine Creek. Surveying up or down a slope with a chain is difficult, if not impossible. Plus, measuring directly along the ground up and down short, steep slopes would have considerably shortened how far south the fifteen-mile line extended, something the Pennsylvania commissioners vociferously opposed. Dixon’s men replaced the Gunter’s chain with a wooden rod called a level that was twenty-two feet long.

  To measure the distance from the top of the creek bank to the water’s edge as a straight rather than sloped line, two chain carriers held a level, one man at each end, so that neither end was higher or lower than the other. Two more crewmen stepped into place, holding one end of a second level directly beneath the front end of the first level. As the crewmen repeated this process, Dixon and his circumferentor kept them on course by aligning the men with a stake placed on the meridian across the creek. It took the crew four levels, or steps, to reach the edge of Brandywine Creek closest to Harlan’s house.

  Brandywine Creek loops around near the Harlan house. Before Dixon’s men had surveyed a mile, Mason noted that they’d splashed across the creek three times. That meant the crewmen had to work in sopping-wet leather shoes or boots and wet wool pants, which may not have dried out during the day, due to chilly air temperatures. Most colonists owned few changes of clothes and only one pair of shoes; changing outfits frequently was not an option. So the waders squelched when they walked, and their legs itched as wet wool chafed their skin. A long hike in these conditions was uncomfortable, as was using the difficult-to-maneuver twenty-two-foot-long levels. After crossing Brandywine Creek once, the crew switched to less cumbersome levels that were only sixteen and a half feet long. As they proceeded south, the men became an efficient and precise survey team.

  Periodically, Mason observed the stars to confirm that the line was still true to the meridian of Harlan’s garden (or to determine how the line needed to be shifted if it had veered off course). On April 5, he noted with satisfaction that he had “Proved the Meridian and found it very exact.” In addition to checking their course, Mason and Dixon also had to check their Gunter’s chain. Repeatedly pulling the chain taut could cause the wire circles at the end of each link to stretch slightly, making the chain inaccurate. Mason and Dixon measured the links’ length against a three-foot-long brass rod. They reshaped any links that had lengthened. On April 5, Mason “Found the chain a little too long. Corrected it.” When he measured the chain again on April 9 and 12, it was exact. The Penns and Lord Baltimore had hired Mason and Dixon as the best men for the job, and the best is what they got.

  By April 12, the crew had traveled over fourteen miles. Now was the time to account for the fact that their starting point, at the observatory in Harlan’s garden, was already 10.5 seconds south of Philadelphia’s southernmost point. That distance had to be included in the overall length of their fifteen-mile-long line south. Mathematically, Mason converted the seconds into yards. He found that 10.5 seconds of a degree of latitude was equal to 357 yards. This distance is more than three and a half times the length of a football field. While that may not seem like much, if the line were placed that much too far south and extended west over the 233-mile-long distance, the acreage added to Pennsylvania’s area would add up. In fact, if the acreage involved were reconfigured as a chunk of land rather than a long, thin strip, it would occupy an area the size of Disney World or the city of San Francisco. The Maryland commissioners would never have ceded that much land to Pennsylvania.

  IT TAKES THE EARTH one year to orbit the sun. Because Earth’s axis is tilted, during half of the year, one hemisphere receives more sunlight than the other, creating the summer season. Earth’s tilt also affects the seasonal visibility of certain stars. For example, in December 1763, when Mason and Dixon first began observations in Philadelphia, Capella, one of the brightest stars in the sky, quickly caught their eyes. In the Northern Hemisphere, Capella is a star of the fall and winter sky and would not be visible in July.

  These are some of the constellations and stars in the Northern Hemisphere that Mason and Dixon regularly observed during different seasons. In these diagrams, other constellations have been omitted in order to highlight those especially important to the surveyors. But Mason and Dixon had to find their stars from among the thousands that were visible.

  East and West are not labeled incorrectly on these seasonal sky maps. A sky map represents the celestial sphere. To orient a sky map, face north. Hold the sky map above your head, as if you were looking up at the stars. Rotate the sky map until its label for North points toward north. East and west are now properly located.


  During the summer, Earth’s tilt and orbital position placed Capella below Mason’s horizon. Seasonally, Mason and Dixon adjusted which stars they observed according to their visibility. The North Star, also called Polaris, is almost straight north of Earth’s axis. It is unaffected by the annual orbit and is visible in the Northern Hemisphere year round, as are the stars that closely surround it.

  Mason then converted 357 yards to chains, arriving at the figure 16.23 chains. Dixon added this to the number of chains he and the chain bearers had already measured southward from Harlan’s garden. Together, the figures added up to 15 miles, 2 chains, and 93 links. The crew’s journey south was complete. The end of the fifteen-mile line was on squishy, damp land owned by a man named Alexander Bryan.

  During the next week, the crew returned to Harlan’s farm, dismantled the observatory, and packed the instruments into four wagons — Mason employing “five Laborers in carrying one of the instruments,” most likely the zenith sector. Then they returned to the end of the fifteen-mile line, where five men, hammering in the rain, reconstructed the observatory. Meanwhile, Mason and Dixon rode to Philadelphia, where they met with the commissioners to report their progress and receive further instructions.