384
EXPOSITION AT VIENNA.
into the walls to receive the end of each girder, and distributes its weight over several bricks.
A second form of floor, employed where it is desirable to
View from above.’
save room, occurs in several buildings in Vienna, but not so generally as the last. Girders are employed as before, but support, in this case, cross-pieces of iron, which, in their turn, receive rods of the same material parallel to the girders, and placed between them. The resulting network is bound together with wire, and hollow bricks are laid upon it in cement. The whole thickness of this construction is about nine inches.
For fire-proof passages connected with stairways, or built on the sides of court-yards, it is customary to lay a girder
Cross-section through girders.
parallel to the wall, with its ends supported by the two adjacent w r alls alone. It is then tied firmly to the first by several iron rods, and a segmental vault is sprung from girder to wall, as before described, of hollow brick. Such passages are very substantial, if properly made; but are otherwise excessively dangerous. From insufficient strength in the tie- rods, an accident of the most distressing nature occurred a year ago here. Some heavy weights thrown violently upon such a passage connected with a stairway, tore the ties