NATURAL HISTORY BUILDING 73 



have in part been described in connection with those parts of the 

 building in which they are located. 



Closing the large openings in the ground story between the east 

 and west ranges and the east and west wings, respectively, which 

 measure 12 feet wide by 15 feet high, are doors and transoms of 

 small lights of glass framed in steel and so subdivided and hinged 

 that any part or all of the structure may be opened. The corre- 

 sponding though smaller openings between the ranges and the north 

 wing at the entrance lobby have double doors of large plates of glass 

 set in bronze frames. The three partitions dividing the construction 

 and repair shops along the south side of the east wing in the ground 

 story have communicating openings 8 feet wide by 10 feet high, and 

 there is another opening of the same size giving access to this suite 

 of rooms from the corridor in front of the boiler room. All of these 

 are provided with single-leaved doors of vitribestos framed and 

 stiffened by steel bars and angles, hung on an inclined overhead 

 track, and arranged to close automatically by gravity in case of fire 

 through the melting of a fusible link in the rope by means of 

 which they are held open. As they are intended to be kept generally 

 closed, each has a small wicket gate for ordinary use. Tlie audi- 

 torium entrance doors and those at each end of the adjoining lobby, 

 all double-leaved, occupy semicircular-headed openings of approxi- 

 mately the same size, but the former are of black walnut with a 

 transom, while the latter are of steel and the doors themselves fill 

 the entire opening. There are double steel doors in the walls closing 

 the ends of the two main corridors in the west wing of the ground 

 story, and each of the two rooms at the outer end of this wing has 

 double steel-covered doors on the side facing the wagon entrance in 

 addition to a door of the typical pattern at the principal entrance. 

 The small rooms in the several stories on the south side of the south 

 pavilion are all provided with wood doors, but the twelve openings 

 occurring between this pavilion and the three wings in the third and 

 attic stories are occupied by hea"\^ double steel doors. 



The typical room doors used in the ground and third stories are 

 7 feet high and of two widths, 3 feet 6 inches and 3 feet, the former 

 being the width of the entrance openings in the corridor walls and 

 the latter that of the communicating openings between rooms. The 

 total number of doors of this pattern is slightly in excess of three 

 hundred. It was the original intention to have them all of steel, 

 but for reasons of economy wood was substituted for about one-third 

 of the number. In the distribution of the two kinds, metal has 

 been selected for the corridor openings and wood for the communi- 

 cating openings, with the following principal exceptions : All of the 

 typical entrance doors in the east and north wings in the ground 

 story are of wood, since the fire risk is not serious in either of these 



