20 UNITED STATES NATIONAL MUSEUM 



introduce many interior piers and columns, which are arranged in 

 one or more rows. The former, which are confined to the basement, 

 are of brick ; the latter are of steel enclosed in terra cotta. The story 

 heights in the clear are 18 feet for the basement, 20 feet for the first 

 story, 19 feet 6 inches for the second story, and 12 feet for the attic 

 story. 



The length each of the east and west wings in the inside is 216 feet 

 1 inch, and that of the north wing 205 feet 2 inches measured through 

 the middle. All are approximately 116 feet wide. As it would be 

 impossible to light this entire width from the sides a large skylight 

 has been introduced in the roof of each wing, covering the central 

 space in the first story to a width of about 50 feet and a distance of 

 between 16T and 168 feet from the wall of the south pavilion. In 

 this manner are formed three great halls which break through the 

 upper stories and are surrounded by broad aisles on the sides and at 

 the outer end, the line of demarcation being marked by rows of large 

 piers. The floors of the second and third stories and the lofts corre- 

 spond in position and width with these aisles, being bounded on the 

 inner sides by the walls of the light wells. The basement on the 

 other hand is entirely ceiled over. 



Each of the ranges, including both arms, has a total interior length 

 of 316 feet 10 inches, and as the width between walls is only 54 feet 2 

 inches their lighting is amply provided for by the windows. 



The first and second or exhibition stories, except for the few struc- 

 tural walls before mentioned and certain screen walls, have been in 

 no way subdivided, but the basement and third story are extensively 

 partitioned to meet the requirements for the storage and study of 

 collections, the mechanical plant and the work shops. Circulation 

 around each story is continuous and unobstructed. 



To permit of uniformity in the installation of cases in the exhibi- 

 tion stories, the wings and ranges have been constructed on a unit 

 basis of length measurement, which is constant throughout. This 

 arrangement, which also lends itself to the room divisions in the 

 other stories, has been facilitated by the uniformly straight horizontal 

 lines of the inner surfaces of the walls. The length of this unit, 

 which is 18^ feet, is the distance from center to center of adjacent 

 wall piers, and also of the interior structural piers and columns in 

 the several rows. 



The provision is therefore for a single window in each unit, al- 

 though in the third story of the wings a granite mullion divides the 

 outer openings into double windows. In the first and second stories 

 the openings have been given a width of 11 feet 6 inches as compared 

 with T feet for the width of the intervening piers, and a maximum of 

 glass surface has been secured through the use of light metal framing. 

 The basement openings are 10 feet wide. In the length of the f agade of 



