The thing principally to be considered, in order to give a Relievo to Painting, is the Ground: In which, it may be observed, that the Terms or Extremes of Bodies which have convex Surfaces, will usually show themselves, even though both the Body and the Ground have the same Colour. Now the reason of this is, that the convex Terms, or Contours of Bodies do seldom receive their Light in the same manner as their Ground, even when the same Light is found to illumine them both; so that the Con- tours become frequently either brighter, or more obscure than the Ground on which they are seen: But shou'd it happen, that a Contour besides having the same Colour, shou'd likewise be illumined, or obscured in the same Degree, with its Ground; in that case, the Contour must inevitably be lost, and the Figure remain indistinguishable. 'Tis for this reason, that a Painter can never be too cautious in his Grounds; nor ever avoid this uniformity of Lights and Colours with too much Study: For, as 'tis his chief aim, to show his Figures rais'd, and advanced from the Ground of his Painting, and as this Practice is found to have a quite contrary effect, to give into it, wou'd be to frustrate his Endeavours, and to defeat himself of his end.