NATURAL HISTORY BUILDING 33 



is also a small door at the base of each stair tower. As in the outer 

 walls, the window openings for the first and second stories are con- 

 tinuous and have a metal panel at the floor division ; they measure 31 

 feet 6 inches high. A minor reveal on the outside of the wall piers, 

 1 foot 4:^ inches deep, carries around both sides and over the heads of 

 the windows. The window openings of the third story are 7 feet 

 high. 



INTERIOR STRUCTURAL FEATURES AND ROOFS OF THE WINGS AND 



RANGES 



In order to provide the large open spaces contemplated by the 

 general plan, but few interior walls having a structural relation to 

 the building have been introduced in the wings and ranges, nearly 

 all subdivisions being effected by means of subsidiary partitions. 

 Such walls, in fact, occur only between the wings and the ranges, 

 between the wings and the south pavilion, and, in the ground story, 

 between the north vestibule and lobby and between the lobby and 

 the body of the north wing. Within the south pavilion, however, 

 many structural features exist as described elsewhere. 



As additional supports for the wide and heavy floors resort has 

 been had to numerous piers and columns of masonry and steel, 

 which are disposed in a single regular row lengthwise through the 

 ranges and in two or more rows through the wings. The steel col- 

 umns where not actually embedded in walls have a fireproof covering 

 of terra cotta, producing piers, and both these and the masonry piers 

 are finished to correspond with the finish of the walls. In the 

 ranges, where the width is not so great but that the lighting may 

 be entirely obtained from the sides, the successive floors are un- 

 broken, but in the much wider wings it has been necessary to pierce 

 the middle part of the several floors above the first story in order 

 to obtain light from overhead. 



Ground story. — The concrete floor base of this story rests directly 

 on the ground and on the top of certain tunnels in which heating 

 and other mains are carried. The finished floor surface was planned 

 to have a uniform grade of +14, but in order to reduce the height 

 of the window sills to a convenient level for the tables in the labora- 

 tories, it became necessary to raise the grade generally, though not 

 everywhere, to the extent of 3 inches. The transition from one leA^el 

 to the other at places where the two adjoin has been accomplished 

 by a gradual sloping of the floors. 



The great span and weight of the first floor have rendered neces- 

 sary correspondingly heavy supports which consist of brick piers, 

 except in the north entrance lobby where steel columns have been 

 used. The spacing of the piers in each row conforms, with few 

 80120°— Bull. 80—13 3 



