190 THE FINE ARTS. 
purpose of allowing objects to sink into the ground and to arise out of it, 
the floor must open at the places required without the spectators hearing 
or seeing it, and the adjacent parts of the stage must be as firm as before. 
For this purpose the following contrivance, represented in jigs. 6 and 7, is 
employed. All the panels of one range are slipped into grooves in the tie- 
beams; but for the last movable panel of each side the grooves slope down- 
wards, so that the panels can be thrust close underneath the fixed part of 
the flooring, and then pass along horizontally again to the side walls 
of the theatre. The lever d (jigs. 6 and 7) is so contrived, that when in its 
place at c,it keeps the panel horizontal and even with the rest of the stage ; 
but when it is slipped out, the panel falls to the level of the sloping grooves. 
Rings are fixed on the under side of the movable panels. If now the 
stage is to be opened at any spot, a rope is simply run through the ring of © 
the last panel that is to be shifted, and is then carried over the cylinder 
of the lower windlass, N (jig. 3). If by shifting the lever the first 
movable panel be let fall down to the sloping grooves, then by turning the 
windlass the last movable panel to which the rope is attached will shove all 
the rest along, and as many panels will be thrust under the solid stage as 
are necessary to make the opening required. When the opening is to be 
closed again, a rope passed through the ring of the first movable panel 
and over the opposite windlass, N (jig. 3), draws all the panels into their 
places again, so that the last one can again be secured by means of the 
lever. If there is to be a descent through the stage, the panels are shoved 
back far enough to admit the platform into the stage; as soon as the 
descent is made, the panels are thrust back into their places and the stage 
closed over it. When an ascent is to be made, the panels are first thrust 
back to form the opening, into which the platform is then raised. 
The side-walls of the theatre are lined throughout with boarding, H (jigs. 
1and 2) in such a manner that an empty space remains, in which the counter- 
weights, J, of the drop-scenes can play up and down. These counter-weights 
consist, as is shown in pl. 25, jigs. 24, 25, and 26, of disks of metal a a, 
which, according to the weight required, are stuck on the rod d d; 
and they are attached by the ring ¢ to the running-ropes of the drop- 
scenes. These counter-weights must weigh together the same as the scenes, 
so that in drawing them up and down there is only the friction to be over- 
come. 
d. The Framework of the Roof. Vf the framework of the roof of a 
theatre be not made of iron, as is now usually the case, but of wood, care 
must be taken to obtain, by employing as little wood as possible, a solid 
hanging and horizontal framework ; since the framework of the roof has to 
support besides its own weight, that of the various flies and the rigging-loft 
floor as well as of the drop-scenes, hanging-scenes, &c. An example of an 
iron roof-framing is furnished in p/. 26, jig. 26, which represents the roof of 
the Théatre Francais. Figs. 27-81 exhibit its details. Another specimen 
of iron roof-framing is given in that of the Cirque Olympique in Paris ( fig. 
35, and details in jigs. 836-43); jigs. 1 and 2 also contain examples of such 
iron frame-work. The details of a wooden roof-framing are shown in the 
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