Charles Mason's Journal


A PDF of the transcribed full journal can be downloaded here. A remarkable document, originally running to 364 pages, it is most striking not so much for Mason's descriptive asides, the most interesting of which are reproduced or summarised in M&D, but in showing the extent of physical and computational drudgery involved in accurate geodesy in the 18th C. Page after page of calculations, often to seven places of decimals, and week after week of near-identical entries, attest to the meticulous professionalism of M&D, who had to time their observations with a watch that had no second hand.

The journal is not a facsimile and does not contain Dixon's map, which can be viewed and downloaded here, but does provide an almost obsessively detailed account of the historical context, correspondance from the principals (including a wonderfully patronising letter from Nevil Maskelyne, then Astronomer Royal, on how they should make their measurements), and an analysis of the celestial mathematics involved. From the introduction:

"At times Mason and Dixon worked under unusual and adverse circumstances, for example, on Christmas Day, and in snow two feet deep, and in temperatures as low as 22 degrees below zero F. Their task was carried out in frontier country without benefit of modern methods and conveniences. But, after two hundred years, checks by the most refined methods of geodesy attest to the mathematical excellence of their accomplishment."

1767 Oct 9

Continued the Line to a High ridge. At 231 miles 20 chains Crossed a War Path. At 231 miles 71 chains Dunchard Creek. This Creek takes its name from a small town settled by the Dunchards near the Mouth of this Creek on the Monaungahela; about 7 or 8 Miles North of where we crossed the said River. The Town was burnt, and most of the Inhabitants killed by the Indians in 1755. At 232 miles 43 chains crosses Dunchard's Creek a second time. At 232 miles 74 chainscrossed Ditto a third time. This day the Chief of the Indians which joined us on the 16th of July informed us that the above mentioned War Path was the extent of his commission from the Chiefs of the Six Nations that he should go with us, with the Line; and that he would not proceed one step farther Westward.'


"1766 June 22 (Sun.)
Went to see Fort Cumberland: It is beautifully situated on a rising ground, close in the Northwest fork made by the falling in of Wills Creek into Potowmack; The Fort is in bad repair; has in it at present only 10 Six Pounders. Going to the Fort I fell into General Braddock's Road, which he cut through the Mountains to lead the Army under his command to the Westward in the year 1755, but fate; how hard: made through the desert a path, himself to pass; and never; never to return."

Capt. Shelby

"1765 Oct 25
Went to Captain Shelby's to desire him to go with us on the North Mountain for to show us the course of the River Potowmack Westward.
1765 Oct 26
Packed up our Instruments and left them (not in the least damaged to our knowledge) at Captain Shelby's. Repaired with Captain Shelby to the Summit of the Mountain in the direction of our Line, but the air was so hazy prevented our seeing the course of the River.
1765 Oct 27
Captain Shelby again went with us to the Summit of the Mountain (when it was very clear) and showed us the northernmost bend of the River Potowmack at the Conoloways [...]"

Last Entry

1768, Sept 11:
At llh 30m A. M. went on Board the Halifax Packet Boat for Falmouth. Thus ends my restless progress in America.
Mason & Dixon Alpha Guide
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