Mason and Dixon a Line [pp. 61-69]

64 MASON AND DIXON'S LINE.
peninsula were to be run, after cutting broad vistas (so called by
the surveyors, and afterwards by Mason and Dixon, as well as by
Maskelyne, the astronomer royal*) through the forests, they ran
their straight lines by sighting along several poles placed in advance, intending to locate the lines between the established points
more carefully at some future time. Thus they established the
tangent point. This work occupied nearly three years; but the
magnates of the day, like many now-a-days, imagined there was
not science and energy enough at home, and so, on the 4th August,
1763, the Penns and Lord Baltimore employed in England Charles
Mason and Jeremiah Dixon, two mathematicians and surveyors,
to take charge of the work. They arrived in Philadelphia November the 15th, received their instructions from the commissioners December the 9th, 1763, and proceeded to the work assigned
them, in connection with some of the old surveyors. They brought
with them a ifull supply of the best instruments of that day;
among others, for astronomical observations, an excellent sector,
of six feet radius, which magnified twenty-five times, belonging
to the Hon. Mr. Penn, the first which ever had the plumb line
passing over and bisecting a point at the centre of the instrument.
They brought also excellent standard chains and brass standard
measures of five feet, provided by the Royal Society.
Bancroft speaks of Mason and Dixon as having run the line in
1761. It was not commnenced by them till 1764, and not completed by them till 1767, and not inally marked till 1768. See
-Bancroft, vol. 2, p. 396, (Latrobe's address.) Mason and Dixon
first proceeded to determine the latitude of the southernmost
point of the city of Philadelphia, which was the north wall of
the house then occupied by Thomas Plumstead and Joseph Huddle, on the south side of Cedar Street. It is recorded in their
journal that in November, 1763 they employed a carpenter to
construct an observatory in the south part of Philadelphia. On
the sixth of January, 1764, they determined its latitude 39 deg.
56 min. 29 sec. N. This was the first astronomical calculation
and the first observatory in America.
They then carefully examined the lines run by their predecessors, which they adopted as correct. Hlon. J. H. B. Latrobe of
Baltimore, in his address before the Pennsylvania Historical Society, in 1854, remarks:
"So far as the work of the old surveyors went, Mason and
Dixon did not seem to have mended it; for they recorded in their
proceedings of November 13th, 1864, that the true tangent line
as ascertained by themselves, would not pass one inch westward or
eastward of the post mawking the tangent point set in the ground
by those whom they superseded." In the autumn of 1764 they
ran their parallel of latitude west to the Susquehanna, thus commencing the famous line which bears their name, and which is
now the boundary between Pennsylvania and Maryland. In 1764
* Royal Soc. Philosophical Transactions, vol. 58.