Mason and Dixon arrive in America
(WHTM) – Over 250 years ago today, Charles Mason and Jeremiah Dixon arrived in Philadelphia to begin their survey of the dividing lines between Pennsylvania and Maryland.
It would take them almost five years to complete the work.
The real land surveying could not begin until the spring of 1764. Mason and Dixon spent much of the winter figuring out where to begin.
The east-west dividing line was to be measured along a latitude of fifteen miles south of the southernmost point of Philadelphia. Mason and Dixon had to determine the precise latitude, which involved a lot of math and a lot of measurements of the movement of the stars.
Most of them were performed by looking through astronomical instruments, lying on their backs, in the dead of winter, at temperatures well below freezing. No one said being a surveyor was easy.
Having established the starting point of the “west line,” Mason and Dixon spent 1764 surveying a completely different frontier. It was the tangent line: the north-south border between Maryland and Delaware, which at the time was part of Pennsylvania.
Both mathematically and geographically, this was the most difficult part of the investigation, and one can’t help but wonder if they tackled it first because they wanted to eliminate it.
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Mathematically, it was difficult because they were measuring a diagonal or a tangent. This meant that instead of just following a line of longitude, they had to calculate everything using trigonometry. (Then they checked their measurements with more star observations.)
Geographically, they had to cross rivers and streams, travel through wetlands and make their way through forests. (A team of men with axes cleared a path 8 to 9 feet wide for Mason and Dixon to take their measurement.)
In 1765 they started on the West Line. It took them until October 9, 1767 to complete their survey, 233 miles later.
But they still had one job to do: create about 200 copies of a map and plan of the survey line. Even with the help of the printing house, it took a long time. So Charles Mason and Jeremiah Dixon finally boarded a ship to return to England on September 11, 1768, nearly five years after first setting foot in Pennsylvania.