« SebelumnyaLanjutkan »
t, place the four upright logs of the table, of what In order to paint upon a plane a deformed copy
base of the cylinder, or else cut off two small equal
from R to the extremities and divisions of the base a, Of the Anamorphosis, or reformation of distorted images. points '';', h, i, k, and the arch of the base in l, m,
b, c, d, e, cut the remotest part of the shadow in the
F, G, H, I, K, and through every intermediate order
easily be effected by one person placing himself in any
tion. Bettinus has illustrated this method by drawings
most generally occur. It is, however, true, and the in-
Fig. 39. and 40.
telligent reader will see, that the two theorems on which cated by every mathematician who had taken the trouble the whole rests, include every possible case, and apply with to consider the subject. They are sufficient not only equal facility to pictures and originals in any position, for directing the ordinary practice, but also for suggestalthough the examples are selected of perpendicular pic- ing modes of construction for every case out of the comtures, and of originals referred to horizontal planes, as mon track. And a person of ingenuity will have a being the most frequent. The scientific foundation be- laudable enjoyment in this, without much stretch of ing so simple, the structure need not be complex, nor thought, inventing rules for himself; and will be betswell into such volumes as have been published on the ter pleased with such fruits of his own ingenuity, than subject : volumes which by their size deter from the in reading the tedious explanation of examples devised perusal, and give the simple art the appearance of in- by another. And for this purpose we would, with Dr. tricate mystery; and by their prices, defeat the design Taylor, " advise all our readers not to be contented of their authors, viz. the dissemination of knowledge with the scheme they find here; but, on every occasion, among the practitioners. The treatises on perspective to draw new ones of their own, in all the variety of ciracquire their bulk by long and tedious discourses, mi cumstances they can think of. This will take up more nute explanations of common things, or by great num time at first, but they will find the vast benefit and pleabers of examples; wbich indeed do make some of these sure of it by the extensive notions it will give them of books valuable by the variety of curious cuts, but do not the nature of the principles.” at all instruct the reader by any improvements made in The art of perspective is necessary to all arts where the art itself. For it is evident that most of those who there is any occasion for designing; as architecture, forhave treated this subject have been more conversant în tification, carving, and generally all the mechanical the practice of designing than in the principles of geo- arts; but it is more particularly necessary to the art of metry; and therefore when, in their practice, the cases painting, which can do nothing without it. A figure in which have offered have put them on trying particular a picture, which is not drawn according to the rules of expedients, they kave thought them worth communicat- perspective, does not represent what is intended, but ing to the public as improvements in the art; and each something else. Indeed we hesitate not to say, that a author, fond of bis own little expedient, (which a picture which is faulty in this particular, is as blameable, scientific person would have known for an easy corol or more so, than any composition in writing, which is lary from the general theorem), has made it the prin- faulty in point of orthography or grammar. It is geciple of a practical system-in this manner narrowing nerally thought very ridiculous to pretend to write a instead of enlarging the knowledge of the art; and the heroic poem, or a fine discourse, upon any subject, withpractitioner tired of the bulk of the volume, in wbich a out understanding the propriety of the language in which single maxim is tediously spread out, and the principle we write ; and to us it seems no less ridiculous for oneon which it is founded kept ont of his sight, contents to pretend to make a good picture without understandLimself with a remembrance of the maxim (not under- ing, perspective: Yet bow many pictures are there to be stood), and keeps it slightly in bis eye to avoid gross seen, that are highly valuable in other respects, and yet errors. We can appeal to the whole body of painters are entirely faulty in this point ? IŅdeed this fault is so and draughtsmen for the truth of this assertion; and it very general, that we cannot remember that we ever must not be considered as an imputation on them of re have seen a picture that has been entirely without it; missness or negligence, but as a necessary consequence and what is the more to be lamented, the greatest maof the ignorance of the authors from whom they have sters bave been the most guilty of it. Those examples taken their information. This is a strong term, but it make it to be the less regarded; but the fault is not the is not the less just. Several mathematicians of emi- less, but the more to be lamented, and deserves the more nence have written on perspective, treating it as the sub care in avoiding it for the future. The great occasion ject of pure geometry, as it really is ; and the perform- of this fault, is certainly the wrong method that is geances of Dr Brook 'Taylor, Gravesande, Wolf, De la nerally used in educating of persons in this art: for the Caille, Emerson, are truly valuable, by presenting the young people are generally put immediately to drawing; art in all its perspicuous simplicity and universality. and when they have acquired a facility in that, they are The works of Taylor and Emerson are more valuable, put to colouring. And these things they learn by rote, on account of the very ingenious and expeditious con and by practice only; but are not at all instructed in structions which they have given, suited to every pos. any rules of art. By which means, when they come to : sible case. The merit of the first author has been uni make any designs of their own, though they are very versally acknowledged by all the British writers on the expert at drawing out and colouring every thing that subject, who never fail to declare that their own works offers itself to their fancy; yet for want of being inare composed on the principle of Dr Brook Taylor ; structed in the strict rules of art, they do not know how but any man of science will see that these authors have to govern their inventions with judgment, and become either not understood them, or aimed at pleasing the guilty of so many gross mistakes; which prevent thempublic by fine cuts and uncommon cases; for without selves,, as well as others, from finding that satisfaction exception, they have omitted bis favourite constructions, they otherwise would do in their performances. To which had gained his predilection by their universality, correct tbis for the future, we would recommend it to and attached themselves to inferior methods, more usual- the masters of the art of painting, to consider if it would ly expedient perhaps, or inventions (as they thought) of not be necessary to establish a better method for the edutheir own What bas been given in this article is not cation of their scholars, and to begin their instructions professed to be according to the principles of Dr Brook with the technical parts of painting, before they let. Taylor, because the principles are not peculiar to him, them loose to follow the inventions of their own uncul. but the necessary results of the theory itself, and incul- tivated'imaginations.
The art of painting, taken in its full extent, consists appear defective in a picture where those objects are exof two parts; the inventive, and the executive. The
actly copied. inventive part is common with poetry, and belongs more Therefore to offer a short hint of thoughts we have properly and immediately to the original design (which some time had upon the method which ought to be folit invents and disposes in the most proper and agreeable lowed in iustructing a scholar in the executive part of manner) than to the picture, which is only a copy of painting : we would first have him learn the most comthat design already formed in the imagination of the ar. non affections of practical geometry, and the first eletist. The perfection of this art of painting depends up ments of plain geometry and common arithmetic. When on the thorough knowledge the artist has of all the parts he is sufficiently perfect in these, we would bave bim of bis subject; and the beauty of it consists in the happy learn perspective. And when he has made some prochoice and disposition that he makes of it : And it is in gress in this, so as to have prepared his judgment with this that the genius of the artist discovers and shows it the right notions of the alterations that figures must un-self, while be indulges and humours his fancy, which dergo, when they come to be drawn on a flat, be may here is not confined. But the other, the executive part then be put to drawing by view, and be exercised in of painting, is wholly confined and strictly tied to the this alone with perspective, till he comes to be sufficientrules of art, which cannot be dispensed with upon any ly perfect in both. Nothing ought to be more familiar account ; and therefore in this the artist ought to go to a painter than perspective; for it is the only thing vern himself entirely by the rules of art, and not to that can make the judgment correct, and will help the take any liberties whatsoever. For any thing that is fancy to invent with ten times the ease that it could do not truly drawn according to the rules of perspective, or without it. not truly coloured or truly shaded, does not appear to We earnestly recommend to our readers the careful be what the artist intended, but something else. Where- perusal of Dr Taylor's Treatise, as published by Colson fore, if at any time the artist happens to imagine that in 1749, and Emerson's published along with bis Ophis picture would look the better, if he should swerve tics. They will be surprised and delighted with the ina little from these rules, he may assure himself, that the struction they will receive; and will then truly estimate fault belongs to his original design, and not to the strict the splendid volumes of other authors, and see their friness of the rules; for what is perfectly agreeable and volity. just in the real original objects themselves, can never
P E R
P E R PERSPECTIVE is also used for a kind of picture or stances must have a proportional degradation in like cir- Perspec. painting, frequently seen in gardens, and at the ends of galleries ; designed expressly to deceive the sight by re Bird's eye view in PERSPECTIVE, is that which suppresenting the continuation of an alley, a building, land
eye to be placed above any building, &c. as scape, or the like.
in the air at a considerable distance from it. This is apAerial Perspective, is sometimes used as a general plied in drawing the representations of fortifications, denomination for that which more restrictedly is called when it is necessary not only to exhibit one view as seen aerial perspective, or the art of giving a due diminution from the ground, but so much of the several buildings or degradation to the strength of light, shade, and co as the eye can possibly take in at one time from any silours of objects, according to their different distances, tuation. In order to this, we must suppose the eye to the quantity of light which falls upon them, and the be removed a considerable height above the ground, and medium through which they are seen; the chiaro obscu: to be placed as it were in the air, so as to look down ro, or clair obscure, which consists in expressing the dif into the building like a bird that is flying. In represenferent degrees of light, shade, and colour of bodies, tations of this kind, the higher the horizontal line is arising from their own shape, and the position of their placed, the more of the fortification will be seen,
and parts with respect to the eye and neighbouring objects,
vice versa. whereby their light or colours are affected; and keep PERSPECTIVE Machine, is an instrument by which ing, which is the observance of a due proportion in the any person, without the help of the rules of art, may general light and colouring of the whole picture, so delineate the true perspective figures of objects. Mr that no light or colour in one part may be too bright or Ferguson bas described a machine of this sort, of which strong for another. A painter, who would succeed in he ascribes the invention to Dr Bevis. aerial perspective, ought carefully to study the effects Fig. 45. is a plan of this machine, and fig. 46. is a Fig 45 which distance, or different degrees or colours of light
, representation of it when made use of in drawing distant and 46. have on each particular original colour, to know how objects in perspective. its hue or strength is changed in the several circumstan In fig. 45. a bef is an oblong square board, repreces that occur, and to represent it accordingly. As all sented by ABEF in fig. 46. x and y (X and Y) are objects in a picture take their measures in proportion to two hinges on which the part old (CLD) is moveable. those placed in the front, so, in aerial perspective, the This part consists of two arches or portions of circles cml strength of light, and the brightness of the colours of (CML) and d nl (DNL) joined together at the top ? objects close to the picture, must serve as a measure, (L), and at bottom to the cross bar dc (DC), to with respect to which all the same colours at several di which one part of each hinge is fixed, and the other