MASON and Dixon were meant to be on the Indonesian island of Sumatra on June 6, 1761, to observe Venus passing between the earth and sun, an event that happens twice in eight years and then not again for a century.

But two days after leaving Plymouth, their ship, the HMS Seahorse, was attacked by a French war ship in the Bay of Biscay resulting in the deaths of 11 men and serious wounding of 38 others.

For the surveyors, it meant a month's delay in getting to the spot they had been dispatched to by the Royal Society, eager for them to time the rare astronomical occasion.

Undeterred the pair got to the Cape of Good Hope in South Africa and set up their observatory just in time to observe the Transit of Venus using precision equipment made by Bishop Auckland-born John Bird.

It is the 250th anniversary of the astronomical feat of Charles Mason and Jeremiah Dixon, who hailed from Cockfield, near Bishop Auckland, County Durham.

By comparing their timings of the transition with those recorded from other parts of the world, scientists could determine the scale of the solar system, an important step forward according to Dr John Lucey from Durham University's physics department.

He said an accurate observation would provide a valuable key in understanding the universe.

Dr Lucey said: "Now if we want to know how far a planet is from us we just shine a laser at it but then it required accurate calculations and you had to know exactly where you were on Earth, that's where their skills as surveyors would have given them a great advantage.

"Observing the transit would have been of huge scientific interest and was very important in the advancement of astronomy."

The findings of Mason and Dixon were credited as some of the best at the time and, upon their return to London, they were commissioned by the Penn and Calvert families to resolve their border dispute in America.

Thus the Mason-Dixon line was created with Pennsylvania to the north and West Virginia and Maryland to the south.

After the abolition of slavery in the northern state in 1781, it became the divider between freedom and forced labour.

But were it not for their sterling work on the Transit of Venus, the history of America's borders, and therefore its wars, could be very different.

Away from academia. Dixon was somewhat of a Jack the lad.

His great, great, great, great, great nephew John Dixon described him as such, having uncovered records from Jeremiah's Quakers branch, which revealed his rebellious side.

He was kicked out of the Quakers on October 28, 1760 for "drinking to excess and keeping loose company".

Mr Dixon said: "At that time he was seeing the world. You can picture men at the bar buying him drinks as he regaled them with his tales, and he would have been a well-known character."

Jeremiah was born in Cockfield on July 27, 1733, the son of a wealthy coal mine owner. Apart from his travels, he spent his life in the village, dying there a 45-year-old unmarried man on January 22, 1779.

It is believed he started a relationship with a widow called MArgaret Bland from nearby Butterknowle and the pair had two daughters, Mary and Elizabeth, named after his mother and sister.

County councillor for Evenwood, Pauline Charlton, said Dixon was one of County Durham's most famous sons and plans are being drawn up to mark the 250th anniversary of the Mason Dixon line in 2013.

Mr Dixon said: Perhaps we have too much history and take people like Jeremiah for granted. It is time we celebrated their great achievements."

* The last Transit of Venus was on June 8, 2004, and it will occur again next year (2012) although will not be visible from Europe. The next transit after that will be in 2119.