The Bureau of Construction recognized the fact that the attention of the public is much more concerned in the external appearance than in the details of interior construction. Hence it is that our “construction” may differ considerably from an engineer’s standpoint of a permanent structure, and yet, remembering that all of the edifices must be immediately removed at the close of the Fair, the policy of providing a larger and more comprehensive exposition by means of cheaper construction, will certainly conform to the American idea of “making the best show for the least money.”
The construction is almost entirely of wood, with the exception of the large trusses and domes already mentioned. The ordinary trusses are “combination,” all exterior walls being built entirely of wood, covered and protected by staff. Staff was invented in France, being used largely in the construction of the Paris Exposition of 1878. It is composed chiefly of powdered gypsum, other constituents being alumina and glycerine. These substances are mixed with water without heat and cast in moulds made from the clay models. The color is a milky white, the permanent effects being produced by external washes. All the coloring of the building is under the directions of a chief of color. The casts are shell-like, about half an inch in thickness, and can be made in very large sheets being nailed directly to the wooden construction, and then colored as desired. They are made in all conceivable forms to imitate cut stone, rock face, marble, moulding and carvings. For the lower portions of the walls, which are exposed to rough usage, the material is mixed with cement, thus making it very hard. Staff is impervious to water. The foundations are nearly all of the “spread-foundation” type, consisting of a bottom layer of three or four inch planks, on which rests transverse layers of timbers, figured for the proper load distributed at a ton and a quarter per square foot of ground surface. The sand found at the site may be considered as practically incompressible, except in a few instances where piles are used. The main floor loads have generally been taken as very heavy to allow for exhibits of great weight. All of the large buildings have been designed with a view to realizing as much as possible at the close of the Fair, in way of salvage.
