PREFACE TO THIS TRANSLATION.

Notwithstanding the Art of PERSPECTIVE must be acknowledg’d so highly and indispensably requisite in the Practice of Painting, Architecture, and Sculpture; that in the First of these especially, nothing commendable can be perform’d without its Assistance: Yet such have been the Difficulties and Obscurities met with in the first Attempts, and so great the Perplexity and Confusion of Lines in the Practice thereof; that the best Instructions, hitherto made English, have invited very few to such a Prosecution of this Study, as might render their Performances of this kind, truly valuable.

’Tis something unaccountable, that, among so many learned Persons as have handled this Subject, Priests, Architects, and Painters; very few, if any of them, have given Directions proper for shunning that Disorder and Confusion of Lines, which, in most Instances, must necessarily attend the Execution of their Rules: In all or most of which, the whole Space for the Performance is confin’d between the Lines of the Plan and Horizon; which, where the Scale is small, and the Height of the Eye not very much advanc’d, renders the Work exceedingly confus’d; and where those Lines are coincident, (which frequently happens) the Method becomes utterly impracticable.

This Author’s great Experience in the Practice of Perspective, having furnish’d him with excellent RULES for Shortning the Work, and Obviating the foremention’d Difficulties; he has here very generously imparted them, and especially the latter, in the Tenth and Eleventh Figures. And tho’ on Perusal of the first three or four Plates, this Method may possibly seem the same that some others have before made use of; yet whoever shall diligently observe and copy the Rules and Examples of the succeeding Figures, must necessarily acknowledge the great Advantage this has in a Perspective-Plan and Upright, clear and distinct; whence the finish’d Piece is deduc’d, without the least Incumbrance of the Work. The Explanations of the Rules here given, are short and instructive; and the Architectonical Designs produc’d to exemplify them, Noble and Magnificent.

The Manner of Designing, where the Perspective is drawn on several Ranges of Frames one behind the other, and such Scenes of Theaters whose Grooves lie oblique to the middle Line, is also here laid down: And by our Author’s Method, Horizontal Perspective, or that of Ceilings, is render’d less difficult than the Vertical, or that against an upright Wall. Upon the whole, nothing seems wanting that may make a Work of this nature complete; unless what concerns Designs which are either Circular, or abound with many Columns: For the Performance whereof, the Author, as he promises in the Sixty-fifth Figure, has, in a SECOND Volume, given a Rule more proper for the purpose; which also may possibly be made English in due time, if this Part meet with Encouragement.

What the Author once intended should make a Part of that Second Volume, he afterwards inserted in the Ninety-third and following Figures of this Book: In the last of which, particular Notice should be taken of his Conclusion; That if Painters would not run into inextricable Errors, they ought as strictly to observe the Rules of Perspective, in designing the Figures of Men and Animals; as they do in painting Columns, Cornices, or other Parts of Architecture.

That none therefore be discourag’d in their first Attempts, through 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 insist so long on some things, as might be thought necessary to Beginners) we shall endeavour to speak as plainly as we can to a point or two, most liable to be misunderstood, or to prove a Stumbling-Block at the Entrance; and then add a Word of Advice to such as shall attempt the putting these Rules in Execution.

The Author, in both his Explanations of the first Plate, has given some Account of what he would have his Reader understand, by Designing in Perspective; and a right Conception of this point being of great Use to facilitate the Work, we thought it not improper, to describe something more particularly, what is meant by the Art Perspective: but shall at present speak only of That, which, whether Vertical or Horizontal, is receiv’d on a Flat and Even Superficies; This being of much the more general Use, and, when rightly understood, renders the Difficulties of the Circular or Irregular Surfaces, easy 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 seen from One determinate Point: For tho’ in Works of great Length, Two, Three, or more Points of Sight are sometimes made use of; yet such may more properly be said to be Several Views conjoin’d, than One Piece of Perspective: Of which see the Author’s Opinion, at the End of this Treatise.

In Perspective, the Eye of the Beholder is esteem’d a Point, from whence Rays are suppos’d to proceed to every Angle of the Object. The Wall or Canvas to be painted (which we shall here call the Section) is imagin’d to intervene at right Angles to the Axis of the said Rays, and, by dissecting them, to receive the Appearance of the Object, in greater or less Proportion, as the Section is more or less remote from the Point of Sight. Our Author’s Rule is, That the Distance of the Eye ought to be equal to the greatest Extent of the Object, whether in Length or Height: As, to view a Building that is a hundred Foot long, and fifty high; he would have the Distance a hundred Foot: To view a Tower sixty Foot wide, and a hundred and fifty Foot high; the Distance should be a hundred and fifty Foot. This Distance is not strictly to be understood of the Space between the Eye and the Object, but of the Space between that and the Section, the Plan of which our Author calls the Line of the Plan, or Ground-line; for it’s often requisite, that the Section be plac’d at some Distance before the Object, on account of Projectures of Cornices, and other Parts of the Work that advance, as in the Eighth Figure.

The Place of the Eye, with respect to its Height above the Ground, ought to be such, as is most natural and agreeable to the Object. Thus in Architecture, the Basements and inferior Parts of a Building are improper to be set above the Eye, and their Cornices and Entablatures have but an ill Effect when below it. General Perspectives indeed require the Sight to be taken at a Birds View; and on other Occasions the Place of the Eye may be vary’d: but the best and most general Rule is, not to exceed five or six Foot Height above the Ground. The Height of the Eye above the Ground, thro’ which a Line is drawn, call’d the horizontal Line, is set on by the same Scale of Proportion, as the Design bears to the real Work; and the Point of Sight so plac’d therein, as may render the Object most agreeable. From the Point of Sight, either on one or both sides in the horizontal Line, you are to set, by the same Scale, the Distance you stand from the Section. And by means of these Points of Sight and Distance, and the Measures of the Parts brought on the Lines of the Plan and Elevation of the Section, by the same Scale; all the Examples of this Volume are reduc’d into Perspective; as is manifest on Inspection of the Figures.

What we would add, by way of Advice, is,

I. That you very carefully observe, what the Author understands by Breadth, Length, and Height, in his Explanation of the Fifth Plate, before you proceed to practise on any Figure; otherwise you’ll certainly misunderstand him; especially in the Third Figure.

II. That the Rules of the Tenth and Eleventh Figures be particularly regarded, for avoiding Confusion in the Plans and Uprights.

III. That from the Disposition of the Perspective-Plans and Uprights, with respect to the finish’d Pieces in the Twelfth and many following Figures, you would observe, with what Dispatch the said Pieces may, without the Help of Compasses, be delineated by your Drawing-Square; viz. the Perpendiculars from the Perspective-Plan, and the level Lines from the Perspective-Upright, or Section.

IV. That you would accustom yourself in Works that have many Lines, to make the Perspective-Plans and Uprights for each Part distinct, so as to prevent all Danger of Confusion. Thus you may have one Plan and Upright for the Basement of a Building; and when that is drawn on your finish’d Piece, remove them, and place those of the Body of the House; and when that’s complete, do so by the Attick, &c. always observing so to place the Plan below, and the Upright on one side of your neat Draught, that your Drawing-Square may command each of them; which will mightily shorten your Work.

V. That the Author’s Advice of taking the Figures in Course, be strictly follow’d in the Practice; which will be a great means to render the Whole easy and pleasant.

This is the Sum of what we thought most proper to advertise you; and have only this farther to request, That if any Mistakes may have escap’d the Press undiscover’d, as we well hope there are few or none, you will favourably correct and pardon them.