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ceiling, transitions are produced in regard to light and atmos-pheric effects of the most pleasing character. The dioramais indeed a most perfect scenic representation of nature; byvaried and ingenious contrivances, it is capable of displayingthe greatest difference in its pictures. It is peculiarly adaptedfor moonlight subjects, and for exhibiting such “accidents' 1in landscapes as sudden gleams of sunshine and their dis-appearance. For showing architecture, particularly interiors,it is unrivalled, as powerful relief may be obtained withoutthat exaggeration in the shadows which is almost inevitablein every other mode of painting. Although as yet onlyemployed for purposes of public exhibition, the diorama mightundoubtedly be made use of for the embellishment of suchparts of a building as corridors and the like, where light canonly be obtained from one extremity.

The Diorama in the Regent’s Park, was erected for theexhibition of pictures with the effects we have been describing;and as one of the most interesting and remarkable of the‘ sights of London, ” deserves a passing notice.

The pictures exhibited are each about 72 feet long, and42 feet wide, and are capable of being shifted and exchangedfor others when required. They are placed at distances fromthe spectator proportioned to the angle at which he wouldview the objects in nature ; and by the united talents of theartist and the machinist, the illusion is rendered so perfect,and so true to nature, that the beholder is almost led to doubtthat they are really the effect of art. Thus in architecturalsubjects, as the interior of a cathedral, the whole is at onemoment subdued by gloom, as by the overshadowing of somepassing cloud. The “ long-drawn aisle ” and deep recessesare obscured, all seems about to be buried in darkness, when,in an instant, as though the interruption had passed awaj r ,and the bright light of day was permitted to shine throughthe windows in its full lustre, the Gothic architecture isillumined in the most beautiful manner, the shadows projectedwith force and truth, and the secondary lights producedbeneath the groinings of the roof in all the delicate gradationsof natural reflections. Landscape scenes undergo similarchanges, and admirable effects are produced in the transitionsfrom shade and darkness, to the brightness of light andsunshine.

The elevation of the building was designed by Mr. Nash ;it is of the Ionic order, the basement embellished, withcolumns and pilasters, &c., the centre of which is theapproach to the theatre. The building consists of a vesti-bule and two lateral houses, facing a circular part of theedifice, which may be regarded as the audience - room ofthe theatre, and is occupied by boxes and an open area forspectators. The sides of this circular part are painted andadorned with festooned draperies, and the top is covered witha transparent painting, divided into many compartments, andcharged with medallion likenesses of several eminent artists,Over this semi-transparent ceiling, or inner roof, rises a coni-cal roof, nearly half of which is glazed. The circular partconsists of a wall, two-thirds of a circle, with two smalldoorways, and two large openings to the compartments ofthe scenic theatre. Immediately within this wall, butdetached from it, is another wall, rising from the floor to theinner ceiling, and which, with the floor, revolves on a pivot,beneath. A large square opening, like the proscenium of atheatre, allows the audience to view the pictures.

The Diorama was opened to the public in October, 1823,and has ever since continued to be visited as one of the mostpopular exhibitions in the metropolis.

DIPTERON, or Dipteros , (from the Greek), or Dip-teue, (from the French ), in ancient architecture, a templesurrounded with a double row of columns, forming a sort of

porticos, called wings, or aisles. Vitruvius inform 3 0ll ]ydipteral temples were octostyle; but this he must min general; for they may be also decastyle. I nfl ®Vo 11 ' 1could not have been less than octostyle, as no roo rV< ;3,have been left for the cell. The same author also 0 c oH'that Hermoginus made a very great improvement W ^.jof

struction of dipteral temples, by taking away the gr9 perrange of columns, which occasioned confusion in tn rtive appearance. prP eD ^'”

DIRECT RADIAL, a right line from the eye, P ecular to the picture. . . i pla ne

DIRECTING LINE, the line in which an origin ^would cut the directing plane. coin* 0

Directing Plane, a plane passing through the ¥sight, or the eye, parallel to the picture. t . j- ne p r °’Directing Point, that in which any original

duced cuts the directing plane. j g i

DIRECTOR OF AN original Line, the SIT bthrough the directing point and the )

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spectator.

Director of the Eye , the intersection of the pthe directing plane, perpendicular to the original P jj reC Pthat of the picture, and hence also perpendicular to t ia . gf ising and vanishing planes; since each of the twoparallel to each of the two former. The director ot .is also sometimes called the eye director.

, DIRECTRIX, or Diiugent, in geometry, a tei® s ai'ing the line of motion along which a describent line,face, is carried in the genesis of any plane or solid- _ tii®

Thus, if the line a b move parallel to itself, and a )e %6line a c, so that the point a always keeps upon the ^ yit will form a parallelogram, a B c D, of which the si ^the describent, and a c the diri gent. So, also, if J- a po* 1

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charging arches are eSf’ 13 ? f ve, T hir S e ci .

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charging arch shouh! Ie “ffth of the chord ot y

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principal braces ■ ti ™ 18 ’ tiie same as auxiliary T JDISH-OUT l r term is used by Batty Langley- , jb s,

or to form woJlI f ° r ? coves °f any kind by means_ Dishing-ocx a Va u}ts for plastering upon. wo^lr ‘bs, for plastering cove d work formed / . pot 1

as cradling S Upoa ‘ Tp e term is of the same

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