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EXPOSITION AT VIENNA.
thick, in order to allow six inches of masonry upon each side of the opening! The object of carrying the flues up through the middle wall is to cause as much heat as possible to be retained in the building, and to avoid the protrusion of the chimney into the interior, which would result if it were placed in the side-walls, which are generally of lesser thickness. Whether the neglect of these precautions has anything to do with the constant fires which we hear of at home, as resulting from defective flues, I am unable to say.
Another form of construction in wood, common in the attic, and often occurring also in the basement floors, consists in laying half or whole trees side by side, and pinning them firmly together. Upon these comes a filling and flooring, as above described, for the basement; and, for the attic, a filling and tile pavement. In all these floors, greater solidity is gained, if the ends of the beams rest upon a timber running the entire length of the wall, thus diffusing their weight more uniformly upon the masonry. This is, of course, especially applicable to the case where the wall is diminished six inches in thickness at the point where it takes up the beams.
Another practice, here worthy of note, is the union of the ends of the beams of adjacent rooms, by means of irons passing through the interior of the middle wall. This adds much to the stability of the floors, while these remain, at the same time, isolated by at least six inches of masonry. Further, kitchens are generally provided with a tile pavement as well as the attics. In passages, especially those of school-houses, and in the basement floor of dwellings, baton or cement floors are not uncommon. These are rendered ornamental by the insertion of small bits of stone into the mass before setting, forming regular patterns, and the whole is eventually polished.
These two forms of fire-proof floors are the most common in Vienna, where wood is used. It remains now to speak of iron and masonry, alone or in connection with one another. Where transverse strains occur, wrought-iron is made use of, and only in a few of the cases where there is a pressure in the direction of the length to withstand, is cast-iron considered admissible. Where beams of moderate length are used, railroad iron is often applied here; but for greater lengths, double T or I girders are necessary. In cases where greater