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Optics

perspective, sometimes, science, principles, art, method and vision

OPTICS, (from the Latin, optica) is properly the science of direct vision. In a larger sense, the word is used for the science of vision, or visibles in general ; in which sense, optics includes catoptrics and dioptrics, and even per spective.

In its more extensive acceptation. optics is a mixed mathematical science, which explains the manner by which vision is performed in the eve ; treats of sight in the general ; gives the reasons of the several modifications or alterations which the rays of light undergo in the eye ; and shows why objects appear sometimes greater, sometimes smaller, some times distinct. sometimes more confused, sometimes nearer, and sometimes more remote. In this extensive signification, it is considered by Sir Isaac Newton, in his admirable work called Optics.

Optics make a considerable branch of natural philosophy ; both as it explains the laws of natere, according to which vision is performed ; and as it accounts for abundance of phy sical phenomena. otherwise inexplicable.

Prom optics likewise arises perspective, all the rules of which have their foundation in optics. Indeed. 'racquet makes perspective a part of optics ; though John, Arch bishop of Canterbury, in his Perspectiva Commun is, calls optics, catoptrics, and dioptrics, by the common name per specti ve.

This art, for so it should be considered rather than as a science, was revived, or re-invented, in the sixteenth century. It owes its birth to painting, and particularly to that branch of it which was employed in the decoration of the theatre. ‘Titruvius informs us, that Agatharchus, instructed by tEs chylus, was the first whc wrote upon this subject ; and that afterwards the principles of this art were more distiectiv taught by Democrittts and Anaxagoras, the disciples of Aga that chus. How they described the theory of this art we are not intbrmed. as their writings have been lost; however, the revival of painting in Italy was accompanied with a revival of this art ; and the first person who attempted to lay down the rules of perspective, was Pietro del Borgo, an Italian. Ile supposed objects to be placed beyond a transparent tab let. and endeavoured to trace the images which rays of light, emitted from them, would make upon it. The book which he wrote upon this subject, is not now extant ; and this is the more to be regretted, as it is very much commended by the famous E!mazio Dante. Upon the principles of Peurgmu, Albert

Duren constructed a machine, by which he could trace the perspective appearance of objects. Balthazar Parussi, having studied the writings of Borgo, endeavoured to make them more intelligible. To him we owe the discovery of points of distance, to which all lines that make an angle of 45> degrees with the ground-line are drawn. Soon after, Guido Ubaldi, another Italian, found that all the lines, which are parallel to each other and to the horizon, if they be inclined to the grmiund-line, converge to some point in the leurizontal line : and that through this point, also, a line drawn from the eye, parallel to them will pass. These principles combined, en abled him to make out a pretty complete theory of perspective. Great improvements were made in the rides of perspective by subsequent geometricians, partioularly by Pmfessor Gravesande, and still more by Dr. Ittsuok Taylor, whose prin ciples are. in a great measure, new, and much more general than those of any person before hint, Although Dr. Tay for really invented this excellent method of perspective, vet it is suggested by Mr. Robins. that the stone method was pub lished by Guido Ubaldi in his Perspective, printed at Pesaro, in 1600. In this treatise the method is delivered very clearly, and confirmed by most excellent demonstrations. In the last book, Ubaldi applies his method to the delineation of the scenes of a theatre ; and in this, as far as the practice is con cerned, he is followed by Signor Sabatellini. in his Practica di Fabrica Scene, of which there was a new edition at Ra venna in 16:1S ; and to this was added a second bed:, con taining a description of the machines used tur producing the sudden changes in the decorations of the stage. In the cata logue of the great Sir Isaac Newton's works, at the end of his Life, is a work on perspective, written in Latin ; Xetetoni Dement(' Perspcctiva 1746. Svc). We are in debted to opticians of a much later period for ingenious devices to apply the knowledge they had if optics, and espe cially of perspective, to the purpose of amusement.

For the principles and practice of PERSPECTIVE, sec that article, w here they will be fully treated of.