DIORAMA DIPLOMAC V. 



685 



part of the apparatus is situated in that intervening 

 angle between the two picture rooms, as seen at P, 

 in Fig. 2. The lines K proceed over small pulleys, 

 k, and over leading pulleys, situated at the end of 

 the roof of the building, after which they are attach- 

 ed to the extremities of the blinds F F in order to 

 close or open them. There are five pairs of these 

 blinds in the length of the skylight, although only 

 one pair can be indicated in the figure. The cords 

 marked L, and those marked M, proceed over small 

 pulleys in the roof, and are then attached to the hang- 

 ing blinds. The lower ends of these cords, L and 

 M, are made fast to the lever G H, on opposite 

 sides of its fulcrum ; consequently when the lever is 

 moved on its centre, some of the blinds will ascend 

 and others descend, so as to pass over each other, 

 and produce different tints of light 5 but no precise 

 nor even general rules can be laid down for these 

 motions, as they must depend entirely upon the na- 

 ture of the scene and the intention of the artist. 

 When it is desired to produce the effect of change in 

 the lights and tones of the picture, a man stationed 

 at the winch P (see Fig. 2), turns it slowly round, 

 and thereby depresses the end H of the lever, and 

 thus a rope, proceeding over pulleys and attached to 

 opposite ends of the lever G H, is wound round a 

 barrel turned by a pinion and cog wheel from the 

 winch ; and, as the ends of it pass off on opposite 

 sides of the barrel, a variety of motions may be pro- 

 duced, simply by turning the winch round in con- 

 trary directions. A balance weight is suspended to 

 one end of the lever, G H, for the purpose of a coun- 

 terpoise to the weight of the blinds. The extent of 

 motion which the various coloured blinds may re- 

 quire to have communicated to them, can be obtain- 

 ed by attaching their cords to the lever G H, either 

 nearer to, or farther from, the centre of motion. 



We have already stated that two pictures are con- 

 tained in the Diorama ; of these one only is seen at 

 a time, and the scene is changed by causing the 

 saloon containing the spectators to revolve on its 

 axis. This is shown by the plan of the building, Fig. 

 2. A is the revolving saloon with boxes, seats, &c., 

 benches, and a carpeted floor on a gently inclined 

 plane; B B the situation of one of the pictures; C c 

 the situation of the other. D D are two large windows 

 fitted up with ground or semi-transparent glass, ad- 

 mitting a portion of light behind the picture. The 

 saloon is a building of a cylindrical form, with a 

 spacious aperture, at a a, in one side, for viewing the 

 picture through. The doors of admission are situa- 

 ted at S S and Z Z, on the opposite side. The 

 spaces between the opening of the saloon. and the 

 pictures is enclosed above, and on each side, by slight 

 screens, forming a kind of vista (as seen at a a and 

 b b), which, concealing the margins of the picture, 

 increase the illusion, as in panoramic pictures. The 

 floor of the revolving saloon is supported upon a very 

 strong timber frame-work, consisting of a central 

 shaft or axis, o, having twelve timbers, or arms, 

 similar to those at p p, arranged around it, at equal 

 distances, in the manner of radii ; the extremities of 

 these are connected together by upright pieces, and 

 the whole framing further strengthened by diagonal 

 braces and cross timbers, which, proceeding from one 

 arm to the next, are firmly bolted to each, and form 

 a pentagonal framing. The cross timbers serve to 

 carry the bearings of twelve strong iron shafts, which 

 form the axes, to twelve cast-iron wheels, or rollers, 

 two of which are shown at v v. These wheels roll 

 round upon the surface of a circular metal curb or 

 ring, firmly bolted on the top of a course of masonry 

 laid along the top edge of the wall V V, and which, 

 having to support so great a weight, has a very solid 

 foundation many feet below the surface. The cen- , 



tral shaft, o, is furnished with a pivot, or gudgeon, at 

 its lower extremity, which works in a brass step 

 piece, is fitted with adjusting screws, and securely 

 fixed in a pier of masonry. The cylindrical part of 

 the saloon above the floor is composed of a light 

 wood framing, and its roof is also furnished with a 

 gudgeon or pivot in the centre, adapted to turn 

 round in a beam affixed to one of the principals of 

 the main roof as seen at I. / /, shows a skylight for 

 admitting a sombre light through the transparent 

 ceiling of the saloon. The extent of the circle de- 

 scribed by the revolving motion of the saloon, in ex- 

 hibiting the two pictures alternately, forms an arc of 

 about 73 degrees ; and, during the time that the sa- 

 loon is in motion, none of the spectators are allowed 

 to go in or out, but when the opening S is brought 

 into its proper situation, opposite to either of the 

 pictures, one of the two doors S or Z of the saloon, 

 will be found to correspond exactly with one of the 

 door ways respectively marked S or Z, shown in the 

 circular brickwall surrounding the saloon, and will 

 thus open a direct entrance to it. On the outside of 

 this circular wall, a suitable room, at R, is provided 

 for such of the company to wait in as arrive at the 

 moment the saloon is revolving. 



The motion of the saloon is thus effected. A por- 

 tion or segment of a wheel with cogs (ri) is firmly 

 fixed to the central shaft (o), so that its cogs may be 

 engaged with those of a pinion fixed upon a vertical 

 shaft which has a bevelled wheel at its lower ex- 

 tremity. This wheel, again, is engaged with the 

 teeth of another- bevelled wheel, placed in a vertical 

 position ; and, as the axis of this also bears a cog 

 wheel, they revolve together. This train of wheels 

 is set in motion -by a small pinion, whichis immediately 

 operated upon by the turning of a winch, having a fly 

 wheel upon the same axis, to equalize and regulate 

 the power. We ought to mention, that each picture is 

 painted upon several thousand square feet of canvass. 

 Among those which have been exhibited are the in- 

 teriors of 'Canterbury Cathedral, Roslin Chapel, and 

 the Chapel of Holyrood House, the lake of Saarnen, 

 in Switzerland, Brest Harbour, and the Cathedral of 

 Chartres. 



DIOSCORIDES, PEDANIUS ; born at Anazarbus 

 (Csesarea Augusta), in Cicilia, in the first century of 

 the Christian era, a Greek physician, author of a cele- 

 brated work on materia medica, in five books. It is 

 particularly valuable in regard to botany, as most of 

 the medicines which the author mentions are taken 

 from the vegetable kingdom. Two other works are 

 also attributed to him ; the Alexipharmaca, which 

 was united with the Materia Medica, forming the three 

 last books of it, and treating of the poisons in the three 

 kingdoms of nature, and their antidotes ; and th 

 Euporista, which treats of remedies that are easily 

 procured. The best edition of Dioscorides is that of 

 Saracenus (Frankfort, 1598, fol.) ; the best com- 

 mentary is by Matthiolus (Venice, 1565, fol.), 



DIOSCURI; CASTOR and POLLUX, twin-sons of 

 Jupiter, and tutelary deities of wrestlers, horsemen, 

 and navigators. See Castor and Pollux. 



DIP of the horizon is an allowance made in all 

 astronomical observations of altitude for the height 

 of the eye above the level of the sea. 



DIPLOMA (from Wx, I fold up ;) literally, a 

 letter folded but once, and therefore divided into two 

 parts. It is used to signify a document signed and 

 scaled, in which certain rights, privileges, dignities, 

 &c., are conferred. Thus a letter or writing of a 

 university conferring a degree is called a diploma. 

 See Diplomatics. 



DIPLOMACY. The precise time at which the 

 word diplomacy began to be applied to the manage- 

 ment of the mutual relations of independent states 



