NATURAL HISTOEY BUILDING 113 



and on the other by an enclosure of corresponding size, containing 

 the passenger elevators and a room behind them. The intervening 

 space, lighted by the three large windows over the north entrance 

 and measuring 70 feet long by 15 feet 9^ inches wide, is screened off 

 from the main part of the wing by a terra cotta wall, 23 inches thick, 

 with three piercings all of which are 14 feet 4f inches high, the 

 middle one being 11 feet 3 inches wide, and each of the side ones, 9 

 feet 8 inches wide. Between this wall and the adjacent crossrow of 

 piers is a passageway 17 feet 3 inches wide. 



In each of the wings the skylighted area has been mostly screened 

 from the aisles, so that the former is almost entirely illuminated 

 from above, while the latter receive nearly all of their light from 

 the windows. By this means additional wall space has also been ob- 

 tained and definite boundaries have been established for the installa- 

 tion of different classes of exhibits. The introduction of these 

 screens has, moreover, tended to improve the appearance of the in- 

 terior of the wings by virtually carrying down the walls of the light 

 wells to the floor level and thereby separating the high central area, 

 as a great hall, from its relatively low-ceilinged surroundings. From 

 the manner of their construction, however, the vastness of the space 

 enclosed in each wing is in evidence from nearly every point of view. 



In the east and west wings the screens consist of plastered walls 

 built between the piers of the lateral rows and reaching from the 

 floor to the longitudinal ceiling girders which span the piers. They 

 are therefore confined to the sides of the skylighted area, but do not 

 extend its entire length, since on each side the interspace between the 

 pavilion wall and the first pier and that between the end piers of 

 the side row and the crossrow have been left open, partly for appear- 

 ance sake and partly to provide for greater freedom of circulation. 

 In the east wing the screens are built of brick and are 10 inches thick, 

 the attached piers, 3 feet wide, projecting about 7 inches on the inner 

 faces. Measured with reference to these screens, the width of the 

 central hall is approximately 50 feet 6 inches, of the north aisle, 31 

 feet 8 inches, and of the south aisle, 31 feet 11 inches. In the west 

 wing the walls are of reenforced macite and only 4^ inches thick, and 

 the width of the central hall is increased to 52 feet 5 inches with the 

 piers projecting 18^ inches, while that of the north aisle is reduced 

 to 31 feet 2 inches, and of the south aisle to 31 feet 6 inches. 



Picture gallery. — To provide accommodations for the hanging of 

 the paintings of the National Gallery of Art, the screening of the 

 central part of the north wing has been carried out in an entirely dif- 

 ferent manner from that above described. The space enclosed is 

 somewhat longer and narrower, and is also completely surrounded 

 except for the entrance openings. This results from the fact that, 

 80120°— Bull. 80—13 8 



