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Mason & Dixon Line Preservation Partnership
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Bird Transit




Todd Babcock and friends at the Charles Mason marker


John Bird Transit and Equal Altitude Instrument to be restored

Restoration of this important artifact has been adopted by the Maryland Society of Land Surveyors and the Maryland Society of Professional Engineers. To donate in support of the restoration fully tax-deductible private donations from individuals and organizations are being accepted. Click here for donation form

This instrument facilitates the measurement of the horizon thereby informing calculations of distance and time.  Governor Thomas Penn purchased this instrument in 1763  from London's pre-eminent scientific instrument maker, John Bird.  Penn provided the transit to Charles Mason and Jeremiah Dixon for their 1763-7 survey of the boundary between Pennsylvania and Maryland, better known as the Mason-Dixon Line.  In 1769, this instrument was used to observe the transit of Venus across the sun as a means of calculating Earth's distance from the sun. In the early 19th century, the transit was used in the tower of Independence Hall in order to establish high noon for the calibration of the tower clock.  That use probably continued until the 1840s when standard rail time was established and there was no longer a need to set clocks by independent measurement.  Apparently, the transit stayed on the third level of the tower (where the clock works are) until it was “rediscovered” in 1913.  This object is one of the few surviving original Independence Hall furnishings.

Charles Mason Receives Memorial Stone at Burial site

The Surveyors Rendezvous made sure everyone will remember Charles Mason.

A British surveyor, astronomer and scientist, Mason received a posthumous honor Saturday when the Surveyors Rendezvous dedicated an original boundary stone from the Mason-Dixon Line in his memory at Christ Church Burial Ground in Philadelphia.




You can Purchase Prints signed by Brian Tucker on eBay or Email for an address to send check directly.

Brian Tucker MDLPP Signed Prints for sale

Proceeds from the sale of the print will be used to protect and preserve the stones and repair or replace stones that mark the Mason and Dixon Line.




Charles Mason marker and stone at Christ Church

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