36 UNITED STATES NATIONAL MUSEUM 



Third ston^. — The steel framework and terra cotta construction of 

 the floor in this story is the same as in the second story, except that 

 in the ranges it has been necessary to make provision for the truss 

 struts of the roofs. The rows of columns are also omitted from the 

 ranges as the support of the floor above is provided for in the roof 

 construction, though the two columns, one each at the northeast and 

 northwest angle of the ranges, are continued as partial supports for 

 the trusses of the hip roof at those places. 



In the wings the steel columns are disposed as in the first and sec- 

 ond stories, and consist generally of a 15 by f-inch plate stiffened 

 with 3 by 4-inch angles. With the exceptions to be noted, these 

 columns stand just outside the walls Of the light wells to which their 

 covering of terra cotta and plaster is joined, forming attached piers 

 on the floored side of the story. The two corner columns at the outer 

 ends of the east and west wings, consisting of somewhat heavier 

 plates and angles, are slightly out of alignment with the other 

 columns, and with their coverings stand separate from the light well 

 walls. They bear, however, upon the corresponding larger columns 

 and piers of the lower stories, and serve as supports of roof trusses 

 beyond the line of the interior columns. 



Attic story. — Only the wing sections of the attics or lofts are ac- 

 tually floored over, 12-inch I beams spanning between the lower 

 members of the roof trusses and spaced 6 feet 8 inches, carrying the 

 terra cotta floor arches which are of the same thickness as the depth 

 of the beams. As the beams project 1 inch above the terra cotta con- 

 struction, their lower surface is buried to that extent in the rough 

 ceiling of the third story which is finished flush throughout. The 

 structural columns are attached to the walls of the light wells as in 

 the story below. They are, in fact, prolongations of the third story 

 columns and extend to a height of 10 feet 2 inches above the finished 

 attic floor, furnishing attachment for the inner ends of the lateral 

 sections of the roof trusses, intermediate members of which divide tho 

 attic space into cross-sections \S>\ feet in length. 



The range attics are low, serving as air chambers and used for 

 pipes, ducts, etc., and have been left unfloored except for a 2-inch 

 layer of cement on top of the furring of the third story ceiling. 



Roofs. — ^The roofs of the wings consist of low slopes at the sides 

 and ends, the outer ones being covered with slate, and a flat deck 

 which, together with the court slopes, are covered with copper. The 

 skylight, in the middle of the deck of each wing, has a double pitch. 

 The range roofs above the mansard are flat-decked and copper-cov- 

 ered, sloping toward' each side. 



Roof framing. — The roof trusses are spaced 18^ feet on centers, in 

 conformity with the length unit of the building. In the wings three 

 trusses are, in fact, used to span the width of 116 feet between the 



