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Ircen cffRrup-along the Line'Ptf, the Angle QT ^/beingan Angle dfy Degrees,that is, the prdent Variation ofthe Needle, and the LineP q, the present Magne-tick Meridian : forwhich Variation not njakkig any Altawance, he pofitively de-termines, that B has all the Land« the Triangle QVq, more than he ought-tohave ^ and that‘his Ditch ©ught to rnn along the Line P .7.

Tis true indeed,. if the Survey er go the »-hole Surroynd of the Lands A,and B, he will find theil- figure and Contents-exactly agreeable to the Maphere exprefled. But then the Bearings of the Lines are all 7 Degrees disterentfrom the Hearings in the Map, and they will-run-in and out upon tlie-adjacentNeighbouring Lands, and caule endlds difterenees becween iheir Posseflors - asis manifest From the Ligure : Wherein the prickt 'Lines rcprdcnt-the Disogree-ment in the Bearings ot the Lines, pretracted from the point P ; and -weleeA incröaching mrhis Neighboursonthe WestwaFd,as heincroaches upon B, andB’s Eastward' Neighbours incroaching on him, -arid soforward and ciear round.Whereasby a dne allowance sor the Variation of the Needlc, all this Confulionand Dilägreeutent is avoided, and-every thing -hirs right.

Thus, fovlnstance, in the Gale before us, knowing that the Magnetick Vari-ation has caüled the prefent'Magnetick Meridian to Fall in the -Line n q P s,7 Degrees From the North to the’Westward ; to reduce this to the MagnetickMeridian at the time of the- Deren Survey , I nnift make the Meridian of my‘Map, to Fall 7 Degrees - turihe Eastward osomy Magnetick,Meridian • -as we Feethe Line P Q, falls - 7 Degrees to the'Eastward of the Line P q.

What isherdläidon süppositionthat the Magnet had no Variation at thetimeöf the'first Surveyraken, and that it'had 7 Degrees ' Variation Westward at thetime of the fecond Survey, may eafily -be-accommodated to the Suppelal of anyother Variations at the first andfecond ■ Surveys, Mutntis- for knowing 1

the Variations we know their Difference ; and if we know theil- Difierence, thisgives us the Angle Q_P q, by which-we reduce them toeach other. The-bestway therefore to make Maps invariable, constant, and everlasting, were-forthe’ Surveyors, who ufe Magnetick Instruments, to make always Allowance forthe Magnetick Variation, and to protract and lay down their Fiats by the trueMeridian.

‘Perhaps it may be objected, That Surveys may - be taken wichout Magnetick•Instruments, and that therefore this Errorariling from the Magnetick Variation,andChange of the Bearing of Lines, may be avoided. To which I answer,-first,That granting a Survey-may be taken without Magnetick Instruments,-this isnothing against what we have laid down, relatingto Surveys that are taken - withMagnetick Instruments, as the Down Survey actually was, and most Surveys-mprefent arc actually taken therewhh. Secorldly, though a Surfcy may be takentruly without'Magnetick Instruments, so as to stiew-the-exact Angles andLines of the'Plat, ‘and.ednsequently the true Contents, yet this will not givethe true Bearings of the Lines, of fhe w my Position in relation to my Neighbours,orbther parts ofi the Country. This mustbe supplyed by the Magnet, or-some-thing equivalent thereto, a 3 firiding a true Meridian Line on your LandbyGc-lestial Observation. .And I dotibt not but the Ancient/C^fZ/onj- before theiDificov^ry of 'the Magnet, werd förCed'to some stich 0 Expedient in-their Surveys,