The Mystery of the Transit in the Tower
By David S. Thaler, L.S.
April, 2014

A PDF complete with images available from Backsights HERE.

For many years on a table between two globes in the Governor’s Council Chamber on the second floor of the building now known as Independence Hall sat a curious object consisting of a steel and brass telescope mounted on a conical axle, a brass frame, and a spirit level. The National Park Service identified it as the instrument used during the famous observation of the Transit of Venus in 1769.1 It is that, but additionally it may be the most historic American scientific instrument of all and its discovery, or perhaps its rediscovery, is quite a tale.

It is the story of the first geodetic survey in the Americas and the greatest scientific and engineering achievement of the age, all the more thrilling as it involved a mystery. The story began a few years ago when the Walters Art Museum in Baltimore installed a wonderful map exhibit and asked local cultural institutions to contribute. The Maryland Historical Society (MdHS) asked me to look at a map which they planned to loan. When I saw it my jaw dropped – for it was the original map of the Mason Dixon Surveysigned and sealed by the twelve boundary commissioners. I then said, “what else do you have” and became aware that deep in the vaults beneath the society library were stored many of the original documents related to the titanic, eightyyear boundary dispute between Maryland and Pennsylvania and the Mason-Dixon Survey.2 A hunt then ensued to see what else could be found. Little did anyone imagine that one of the only two known artifacts from the first reading and proclamation of the Declaration of Independence would be discovered.

The story actually begins with Sir George Calvert, a Catholic, who was the secretary of state to the Protestant King James I of England (James VI of Scotland, son of Mary Queen of Scots). Sir George had the unenviable task of shepherding the King’s anti-Catholic measures through Parliament. For his loyal service to the Crown he was created Lord Baltimore, a Baron in the Irish peerage, and was also granted land in North America. Calvert first attempted a settlement in Newfoundland, but the harsh weather forced him to abandon the colonial venture. He next tried Jamestown, but was not accepted due to his Catholic faith, and so petitioned Charles I, who had succeeded to the throne, for a province just north of the Virginia colony that he named Maryland in honor of Queen Henrietta Maria.

On June 20, 1632, the royal charter granted to Lord Baltimore included all of the territory from the Atlantic Ocean “unto the true meridian of the first fountain of the River Potowmack” and from the south bank of the Potomac River to include all land “which lieth under the Fortieth Degree of North Latitude.” The grant was limited to lands, hactenus inculta (hitherto uncultivated, i.e., unsettled) by which clause Lord Baltimore would lose what is now Delaware, based on the somewhat dubious claim of prior Dutch and Swedish settlement.

The other player in the story is Sir William Penn who had been a distinguished admiral in the Royal Navy during the Dutch wars. He had loaned the profligate King Charles II the then stupendous sum of 16,000 pounds sterling. In was granted the province of Pennsylvania. Penn was granted all of the land for five degrees of longitude west of the Delaware River from the 42nd down to the 40th parallel of latitude, excluding a “twelve mile circle” around New Castle town in what is now Delaware.

So Calvert, the proprietor of Maryland, was granted from the Potomac up to the 40th parallel and Penn, the proprietor of Pennsylvania, received from the 42nd down to the 40th parallel, to where it intersected a circle twelve miles from New Castle. But the question was—where was the 40th parallel? Unfortunately for the proprietors, seventeenth-century maps were based upon John Smith’s 1608 exploration of the Chesapeake region first published in 1613 in the General Historie of Virginia—and the Smith map showed the 40th parallel too far south. In fact, the 40th parallel of north latitude does not intersect a twelve-mile circle around New Castle but lies much farther north. This discrepancy ignited a border feud that raged for more than eighty years, a high-stakes dispute involving 4,000 square miles of territory. Philadelphia was settled at the limits of navigability of the Delaware River and lay about five miles south of the actual 40th parallel. Depending upon the location of its border, Pennsylvania could have lost both Philadelphia and its all important access to the sea and re-supply.

It was also unclear to whom taxes were due, and violence broke out regularly along the border. In 1736 fifty Pennsylvanians attacked a Maryland farmstead killing one man, and in another famous case, Colonel Thomas Cresap, a Maryland partisan, operated a ferry on the Susquehanna in what is now Pennsylvania. After confiscating land for Maryland and refusing to pay taxes to Lancaster County in what became known as Cresap’s War, he was arrested and dragged through the streets of Philadelphia, where he is reported to have exclaimed to one of his guards, “Damn it Aston, this is one of the prettiest towns in Maryland.”3 To settle the dispute, the Calverts proposed sailing up the Delaware until the 40th parallel could be determined with a sextant, but the Penns argued that their southern border should be no farther than twelve miles north of New Castle ....

For the entire article complete with excellent images and diagrams please view the PDF. Don't pass this by!

Copyright © David S. Thaler, Used with permission by
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