When one White Body serves as a Ground to another, these two Whites, will either be equal, or they will not; If they be equal, then that suppos'd to be nearest you, may be a little obscured, towards its Extremes bounding on the other; But, if the Ground be less White than the Colour laid upon it, then will the latter loosen it self of course from the other, so that you need not have recourse to any Expedient or Artifice whatever.