REPORT OF MR. NELSON L. DERBY.
395
all combustible is instantly inflamed. This is well understood in Austria, as is shown by the building-laws quoted above, which require the separation of these two substances. Where danger of fire might arise from falling sparks,—as in many cases of railroad buildings,—of course a sheet-iron casing has its value; but in general, where fire is liable to occur within, its use, to any great extent, seems inadmissible.
Among the plans to be seen at the Exhibition, my attention was especially directed to those of the new national library at Paris, whose description was appended. I translate a few of the principal particulars. This building is capable of containing (2,000,000) two million books and manuscripts. Its walls are all of masonry, while the floors, roofs, doors and windows are all of iron. To avoid the necessity of steps and ladders, all books can be readily reached by numerous iron balconies, separated from one another by intervals of about six and a half feet, while the carpenters’ work is, in general, replaced by iron throughout the building. The roof is covered by glazed tiles, supported upon iron trusswork, and, at various portions of the same, terraces, affording access to large reservoirs, constantly filled with water, offer additional protection in case of fire. In the large reading-room, containing seats for four hundred and fifty persons, several iron columns, of very small diameter, help to support the roof. These are here in place; but, where there is a large quantity °f combustible matter in the vicinity, such supports are always dangerous. As the Boston fire showed, they bend immediately upon becoming red hot, and let everything liorne by them fall in general destruction ; granite proved little better,—cracking and falling rapidly to powder when attacked by the flames. For magazines and store-rooms,— especially those containing combustible matter, and where a small loss of room is comparatively unimportant,—brick, it would seem, might be used for pillars where these are necessary. Certainly, no other material has shown itself so valuable in case of fire.
Better than the Exhibition, as a field for study, is the city °f Vienna itself; and I cannot do better than describe its finest building throughout, before closing this Report. For lts beauty, the solidity of its construction, its security against