22 UNITED STATES NATIONAL MUSEUM 



The solid contents of the building amount to 11,604,984 cubic feet, 

 and its cost, including the power plant and other mechanical equip- 

 ment, was, therefore, at the rate of 30 cents and a small fraction a 

 cubic foot, which is relatively very low for the construction of a 

 building of such a substantial character. 



In the detailed description of the building which follows the 

 architectural attic is referred to as the third story, while the lofts 

 are "designated collectively as composing the attic story. The term 

 ground story is also employed instead of basement as better denoting 

 the nature and importance of the use of this story, and it is the 

 term which has come to be generally recognized. 



EXTERIOR WALLS 

 FOUNDATIONS AND GRADES 



While the grade of the building site with reference to mean low 

 water mark in the Potomac Eiver at Washington is so low as to 

 have practically interdicted the construction of an underground 

 story, but little difficulty was encountered in providing secure foun- 

 dations without resorting to piling. This was due to the fact that 

 the ground occupied was mainly a natural slope composed of clay, 

 sand and gravel, although on the northern side adjacent to the old 

 Tiber Creek, long since filled in, softer material was found and much 

 deeper excavations were necessary. 



The grade level of the ground about the building was fixed at +11, 

 and that of the basement or ground floor at +14, the former being 

 approximately 4 feet and the latter 7 feet above the grade of B Street 

 north, from which the front of the north pavilion is distant about 

 64 feet. With the natural surface rising toward the south the 

 extent of the excavation for the site increased in that direction, and 

 the south front of the building is faced, beyond a broad area con- 

 taining a drive, by a sloping bank which reaches a maximum level of 

 +23.92 or a height of about 13 feet above the ground level of the 

 building at the foot of the south approach, leading to the main 

 entrance on the first floor. At the sides of the building the em- 

 bankments gradually disappear toward the north. 



The foundations range in depth from an average of +5 at the 

 south to an average of — 2 at the north and an extreme of —8.5 at 

 the northeast comer of the building. They rise to a grade level 

 of +10.5 for the exterior walls and of +12 for the court walls. 

 They are constructed of concrete and consist of stepped footings sur- 

 mounted, in the case of all exterior and other structural walls, by 

 foundation walls, but the interior brick piers rest directly on foot- 

 ings. The width of the footings and the thickness of the walls vary 

 considerably in accordance with the requirements of the super- 



