OF INSTRUMENTS FOR DRAWING IN PERSPECTIVE.

Various have been the methods used to facilitate the practice of perspective, as well for those who understand, as those who are ignorant of that art; and, though some have supposed that the warmth of imagination and luxuriance of fancy, which impels the mind to the cultivation of the fine arts, is not to be confined to mechanical modes, yet upon inquiry they will find, that the most able and accomplished artists are often obliged to have recourse to some rules, and to use some mechanical contrivances to guide and correct their pencil. So great is the difficulty, and so tedious the operation of putting objects in true perspective, that they trust mostly to their eye and habit for success; how well they succeed, we may decide from the portraits drawn by the best artists, and the different judgments formed concerning them. Mr. Eckhardt has well observed, that there is no artist who will be hardy enough to say, that he can delineate by the eye the same object twice with exactness, and preserve a just and similar proportion of parts in each. In one of the figures, we shall find some of the parts larger than in the other-both cannot be right: yet, supposing them perfectly the same, neither may be conformable to nature. Add to this, many situations of an object occur, which no eye, however habituated, can represent with accuracy.

On this account, I have a long time endeavoured to complete an instrument that should give the outline of an object with accuracy. These Essays have now swelled so far beyond my intentions, that I must be as concise as possible. I must, however, acknowledge the valuable hints communicated by Mr. Heywood, and other ingenious men.

The methods most generally in use are. 1. The camera obscura. 2. The glass medium or plane.

3. A frame of squares. The inconveniences and inaccuracies which attend these expedients, induced Sir Cristopher Wren, Mr. Ferguson, Mr. Hirst, my Father, Mr. Watt, Mr. Eckhardt, Pere Toussaint, and others, to have recourse to different contrivances to remedy their defects; of which those by the Rev. Mr. Hirst, my Father, Mr. Watt, and Mr. Eckhardt, are undoubtedly the best; Mr. Eckhardt's and Mr. Hirst's vary but little from each other.

That represented at fig. 1 and 2, plate 32, appears to me far superior to any that have been hitherto contrived; the object is delineated on an horizontal plane, the pencil B, may be moved in any direction, whether curved or straight, with the utmost freedom. By it, the artist may be sure of obtaining the measure of every part of the object with exactness; and this is performed without any loss of time. The instrument may be moved from any place, and brought back to the same with great exactness; and the outline may be formed either of a number of points, or one continued line, at the pleasure of the draftsman.*

That represented at fig. 2, is a simple instrument; it moves with facility in every direction, and the whole operation consists in looking through the sight C, which may be placed in any convenient situation, and moving the pencil B, so that the apex A of the triangle may go over the object, whose outline will be delineated at the same time. by the pencil B.

To lessen the expence and render the instrument more portable I have constructed an instru

*Fig. 1, represents a more simple and useful perspective glass machine than the one referred to by our author in the former editions of this work; this machine was of complex, and costly construction, and by containing many wheels and joints in the framing, the young practitioner found it rather inaccurate and incommodious. IDIT.

ment somewhat similar to that represented at fig. 2, but which moves only in a vertical plane, the board on which the drawing is made being in the same plane with the triangle.

To these may be added the parallel rule, and the perspective compasses. The distance of the rule from the cyc, as it has no sights, must be regulated by a piece of thread tied to it, and held between the teeth.

Fig. 3, plate 32, is a pair of pocket brass perspective compasses, by Mr. Jones, that have been found very useful and convenient for taking readily the relative proportions of buildings, landscapes, &c. and protracting them on the drawing. A, A, are the two legs, made of small tubes about six inches in length; B, B, are two sliding legs moving to different distances out of the tubes A, A; D is a sight piece with a small hole; E, E, are two steel points to take the sights by; F, F, are two more small steel points at the ends of the sliders to mark down the distance on the paper, after an observation; C is an arc with teeth fixed on one leg, by which, and the pinion G, the other leg is moved to the proper angle while observing. This arc is sometimes divided into degrees, and otherwise subdivided by a set of figures, so as to give distances by inspection, &c. according to the pleasure of the purchaser. The sight C, turns down; the sliders B, B, go inwards; the arc takes off, and the whole packs into a small narrow case.* *

*Fig. 1. represents a perspective glass plane, so mounted that the perspective pictures of objects may be taken in a true and familiar inanner, and for a young student is perhaps the best of any hitherto contrived. A represents a glass plate, of about 16 inches high, and 20 inches broad, or of any other suitable or desired dimensions, fixed in a square mahogany frame, and connected to a portable table B, the legs of which may either be made to fold down or take out of sockets. C is a circular thin plate with small holes of different sizes for the eye to observe through in a fixed position; D is a wooden bar for the arm to rest

on while the hand is tracing the picture on the glass. The application of this machine is too evident to require minute description, it is only necessary to remark, that the observer must keep his head steady whilst he draws the representation of the object upon the glass with a black lead pencil, in a manner as if the pencil touched the object itself.

The glass must be previously prepared, by covering it with strong gum water, which when dry will retain the pencil traces, and those gone over with a pen and ink. A sheet of white paper being placed on the glass, the picture may be traced there as with a pencil, and afterwards finished by the proper colours, lights, and shades.

The sight wheel C, has in some machines been made adjustable to different distances from the glass A, and a table of figures or scale applied to the slider, so that the relative propor tions of the diminutions of the picture may be determined previous to the copying.

Instead of a glass plane, a frame of square lines or wires about half an inch in the squares, as represented in fig. A, plate 7, has been applied by some artists, and transferred from observation on paper containing a similar set of squares drawn with pencil on the paper for the delineation.

Another method I wish to suggest, as preferable to any for a young artist objecting to the trouble of the copying glass, is to apply an universal jointed tracing point, A, fig. 3, to be moved by hand over the outlines of the object, while the eye is at C; a small pointed pin is placed nearly under the tracing point, so that any number of desired points may be readily protracted or marked down on white paper fixed on the table, by simply turning down the frame, which may be made to move on hinges for that purpose.

The most easy and familiar Introduction to Perspective, is by James Ferguson, 8vo. ; and Malton's Young Painter's Maulstick, 4to. The best general treatise on Perspective, by Edwards, second edition, 4to. The most concise mathematical treatise, by Brook Taylor, 8vo. EDIT.

FINIS.

ADDENDA,

BY

THE EDITOR.

As this treatise is designed to comprehend a general collection of the most approved methods of surveying. I think the following method of surveying a large estate by Mr. Emerson, and the new method of surveying and keeping a field book by Mr. Rodham, as published in Dr. Hutton's Mathematical Dictionary, 2 vols. 4to. 1796, will be of real information to many surveyors; and, in my opinion, as deserving of practice as any other method I am acquainted with.

TO SURVEY A LORDSHIP, OR LARGE ESTATE OF LAND.

"If the estate be very large, and contains a great number of fields, it cannot be done by surveying all the fields singly, and then putting them together; nor can it be done by taking all the angles and boundaries that inclose it. For in these cases, any small errors will be so multiplied as to render it very much distorted.

1. Walk over the lordship two or three times, in order to get a perfect idea of it, and till you can