Towards the end of the line the terrain got more hilly so Mason and Dixon did not lay markers, but erected large rock groupings or cairns instead. Later, additional surveys done by the United States Coast and Geodetic Survey in 1901 and 1903 replaced the cairns with leftover markers.
Since the last inventory in 1980, several stones have been destroyed or damaged by vehicles. "I took a picture of one stone in October and three months later in January of 1996 a snowplow hit it, broke it and pushed it down into the farmer's field," Babcock says. "It had been on the line for over 200 years. Now it sits in a farmer's barn."
Some damage is due to vandalism. "A lot of times we've seen places where people actually shoot (the stones) with a rifle. You can see marks on the side where they shoot it with a gun," Babcock says.
Although there is nothing scientifically groundbreaking about the calculations made by Mason and Dixon, creating a boundary with almost constant latitude was "a logistical achievement and represented hard core science done under harsh conditions," Knott says.
"When you walk the line you get a better feel of the conditions involved in hauling huge granite monuments 132 miles across hostile terrain," Knott says. "Up, down through streams, through marshes, through all kinds of weather conditions. It's not an easy task for anybody."
At minimum it took a couple of weeks to make each set of observations. "They would be up at night taking their astronomical observations of the stars in temperatures sometimes 20 degrees below zero," Babcock says. They would essentially lie on their backs and look through a six-foot-long telescope measuring the angles between stars and the meridian, the due-north line.
Mason and Dixon actually used instruments made specifically for this project. The zenith sector, designed by Dixon's mentor John Bird, was the most advanced instrument of the day for determining latitude. Bird said it was accurate to within 100 feet.
Babcock and Knott photograph each marker they find on all four sides, and record its color, condition, weathering and the state of the coat of arms.
It is not just the historical importance that drives the team. "I feel a kinship with Mason and Dixon and every time I come out I learn something new about the methods that they used and I have a greater respect for what they went through," says Babcock.
"Cream of the crop of their day," says Dilwyn Knott. "Few people at that time could accomplish what they did."
"Mason and Dixon were surveyors and astronomers, very well educated men of their time and we hope to have credit given where credit is due," says Babcock.
Babcock and Knott have been documenting the stones for ten years. Of the 230 stones that delineate the Pennsylvania and Maryland border, 80 to 90 stones lack GPS coordinates. Although Babcock and Knott say it is a little embarrassing that their project has taken twice as long as the original Mason-Dixon Line they emphasize that this is a hobby for them and that Mason and Dixon were paid.
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