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IN the firſt place we ought to ſet down (as a Foundation) what that is, which we call DATUM or GIVEN; then to conſider the Profit and Utility thereof; and in the third place, to what Art or Science this Tract doth appertain.

The Word DATUM therefore is diverſly defined, for the Antients have defined it after one manner, and later Writers after another, whence it follows that it ſeemeth a difficult thing to give a true Explication thereof; for ſome of them have not delivered the Definition of the Word; but have with much Labour and Trouble ſought certain Proprieties thereof, and ſome others collecting and mingling what hath been