ular ▁line ▁to ▁the ▁western ▁side ▁of ▁the ▁ 1 2 - mile ▁circle . ▁ ▁A ▁" n orth ▁line " ▁along ▁the ▁mer id ian ▁( line ▁of ▁longitude ) ▁from ▁the ▁tang ent ▁point ▁to ▁the ▁Maryland - P en nsylvan ia ▁border . ▁ ▁Should ▁any ▁land ▁within ▁the ▁ 1 2 - mile ▁circle ▁fall ▁west ▁of ▁the ▁north ▁line , ▁it ▁would ▁remain ▁part ▁of ▁Del aware . ▁( This ▁was ▁indeed ▁the ▁case , ▁and ▁this ▁border ▁is ▁the ▁" arc ▁line ". ) ▁ ▁The ▁disput ants ▁engaged ▁an ▁expert ▁British ▁team , ▁astronom er ▁Charles ▁Mason ▁and ▁survey or ▁Jer em iah ▁D ixon , ▁to ▁survey ▁what ▁became ▁known ▁as ▁the ▁Mason – D ixon ▁line . ▁It ▁cost ▁the ▁Cal ver ts ▁of ▁Maryland ▁and ▁the ▁Pen ns ▁of ▁Pennsylvania ▁£ 3 , 5 1 2 ▁ 9 / – ▁() ▁to ▁have ▁ ▁survey ed ▁with ▁such ▁accuracy . ▁To ▁them ▁the ▁money ▁was ▁well ▁spent , ▁for ▁in ▁a ▁new ▁country ▁there ▁was ▁no ▁other ▁way ▁of ▁establish ing ▁ownership . ▁ ▁The ▁Mason – D ixon ▁line ▁is ▁made ▁up ▁of ▁four ▁segments ▁corresponding ▁to ▁the ▁terms ▁of ▁the ▁settlement : ▁ ▁the ▁tang ent ▁line ▁ ▁the ▁north ▁line ▁ ▁the ▁arc ▁line ▁ ▁the ▁ 3 9 ° 4 3 ′ ▁N ▁parallel ▁ ▁The ▁most ▁difficult ▁task ▁was ▁fixing ▁the ▁tang ent ▁line , ▁as ▁they ▁had ▁to ▁confirm ▁the ▁accuracy ▁of ▁the ▁trans pen ins