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Meffieurs Mafon and Dixon perceived that a moft 
inviting opportunity was here given for determining 
the length of a degree of latitude, from the meafure 
of near a degree and half. Moreover, one remark- 
able circumfbmce very much, favoured the undertak- 
ing, which was, that the country, through which 
the lines run, was, for the moft part, as level as if it 
had been laid out by art. 
The agronomical obfervations had been taken 
with an excellent fedtor of fix foot radius, conftrudted 
by Mr. Bird, the firft which ever had the plumb- 
line palling over and bifedting a point at the centre 
of the inftrument. This instrument was lo exadr, 
that they found they could trace out a parallel of 
latitude by it, without erring above 1 5 or 20 yards ; 
in doing which, it Should be obferved, that they ge- 
nerally ufed the fame Stars, commonly 6 or 8. or 10 
in number, at the Several Stations, and made a 
double fet of observations at each Station, with the 
limb of the fedtor turned both to the eaSt and to the 
weft. This fedtor had been fet up at the northermoft 
point of the lines before- mentioned as proper for 
determining the length of a degree of latitude. In 
order to determine the difference of latitude between 
this point and the fouthermoft point of the lines, or 
the amplitude of an arch of a meridian contained be- 
tween their parallels, it was neceftary that the fedtor 
Should be alfo fet up at the fouthernmoft point, and 
the like obfervations repeated there, upon the Same 
Stars, which had already been obferved at the nor- 
thernmoft point. 
This plan of a meafure of a degree in North 
America, Meffieurs Mafon and Dixon Submitted to 
the 
