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PREFACE. to the middle Line, is alo here laid down: And by our Author's Method, Horizontal Perpective, or that of Ceilings, is render'd les difficult than the Vertical, or that againt an upright Wall. Upon the whole, nothing eems wanting that may make a Work of this nature complete; unles what concerns Deigns which are either Circular, or abound with many Columns: For the Performance whereof, the Author, as he promies in the Sixty-fifth Figure, has, in a SECOND Volume, given a Rule more proper for the purpoe; which alo may poibly be made Englih in due time, if this Part meet with Encouragement.

the Author once intended hould make a Part of that Second Volume, he afterwards inerted in the Ninety-third and following Figures of this Book: In the lat of which, particular Notice hould be taken of his Conclusion; That if Painters would not run into inextricable Errors, they ought as trictly to oberve the Rules of Perpective, in deigning the Figures of Men and Animals, as they do in painting Columns, Cornices, or other Tarts of Architecture.

none therefore be dicourag'd in their firt: Attempts, thro' the Brevity or Silence of our Author, (who, writing in a Country where the Principles of this Art are more generally known than with Us, had no need to init o long on ome things, as might be thought neceary to Beginners) we hall endeavour to peak as plainly as we can to a Point or two, mot liable to be miundertood, or to prove a Stumbling-Block at the Entrance 3 and then add a Word of Advice to uch as hall attempt the putting thee Rules in Execution.

Author, in both his Explanations of the firt Plate, has given ome Account of what he would have his Reader undertand, by Deigning in Perpective: and a right Conception of this Point being of great Ue to facilitate the Work, we thought it not improper, to decribe omething more particularly, what is meant by the Art Perpective; but hall at preent peak only of That, which, whether Vertical or Horizontal, is receivd on a Flat and Even Superficies: This being of much the more general Ue; and, when rightly undertood, renders the Difficulties of the Circular or Irregular Surfaces, eay and familiar.

PERSPECTIVE is the Art of Delineating, on a flat Superficies, as a Wall, Ceiling, Canvas, Paper, or the like, the Appearances of Objects, as een from One determinate Point: For tho in Works of great Length, Two, Three, or more Points of Sight are ometimes made ue of; yet uch may more properly be aid to be Several Views conjoin'd, than One Piece of Perpective: Of which ee the Author's Opinion, at the End of this Treatie.

Perpective, the Eye of the Beholder is eteem'd a Point, from whence Rays are uppos'd to proceed to every Angle of the Object. The Wall or Canvas to be painted (which we hall here call the Section) is imagin'd to intervene at right Angles to the Axis of the aid Rays; and by directing them, to receive the Appearance of the Object, in greater or les Proportion, as the Section is more or les remote from the Point of Sight. Our Author's Rule is, That the Ditance of the Eye ought to be equal to the greatet Extent