NATURAL HISTORY BUILDING 35 



3^ inches in the wings and 5 feet 6 inches in the ranges. Tie rods 

 I inch in diameter and about 4 feet 6 inches apart are used between 

 all beams. The tops of all girders are 4^ inches below the finished 

 floor level, and their bottoms including the furring of terra cotta 

 blocks project 21 inches below the rough ceiling of the ground story. 

 The spaces between the beams are filled in with segmental brick arch 

 construction, 9 inches thick, and the rough floor is leveled off with 

 concrete to within 5 inches of the finished floor line. 



The interior upright supports for the second floor consist entirely 

 of I-shaped steel columns, which are 15 inches over both dimensions 

 and built up of single plates 15 inches wide stiffened with 7-inch by 

 3^-inch by f-inch angles, except in certain instances where the plates 

 and angles are slightly lighter or heavier. They are spread at the 

 base and riveted to plates which are in turn riveted to the first floor 

 girders. In the ranges the distribution of these columns is identical 

 with that of the piers in the ground story, but in the wings only the 

 outer rows of ground story piers*, one on each side and one at the end, 

 are represented, an exception occurring at the northern end of the 

 north wing, where there are two crossrows of four columns each. 



Second story. — ^AVhile the girders of the second story floor have the 

 same arrangement and spacing as those of the first story, they are of 

 the single plate type, with the middle web 3 feet deep- and the top and 

 bottom cover plates 14 inches wide by •/« inch thick. In the wings, 

 however, they occur only between the outer and court walls and the 

 rows of columns, leaving the space included within the columns 

 entirely open', the well through which the middle part of the main 

 story in each wing derives its light from the skylights beginning at 

 this level. The girders with their furring project 2 feet 4 inches be- 

 low the rough ceiling of the first stoiy. The I beams between the 

 girders, 12 inches deep, are generally spaced 5 feet 7 inches in the 

 wings and 1 inch less in the ranges. The tie rods, f inch in diameter, 

 are spaced the same as in the first floor. The floor construction is 

 of terra cotta flooring tile, 12 inches thick, topping 5 inches below 

 the finished floor level. 



The steel columns of the second story are identical in construction 

 and position with those of the first story, but differ in a general ^V 

 inch reduction in the thickness of the plates and angles. Those in 

 the wings, however, except the extreme northern crossrow in the 

 north wing, are enclosed in the walls of the light wells, which are 

 partly supported by beams of the same depth as the typical floor 

 beams, attached to the light well side of the columns and 8 inches 

 from them. Similar beams occur at the floor levels of the third and 

 attic stories. The light well partitions are further stiffened in the 

 three stories by double 3-inch by 3-inch by f-inch angle studs secured 

 to the beams and spaced between the columns. 



