NATURAL HISTOEY BUILDING 49 



each light well, 13 feet high by 5 feet wide. On the south side of 

 the first story an opening 16 feet high by 10 feet 11 inches wide 

 frames the entrance vestibule construction. The openings of the stair 

 towers are 13 feet 4^ inches wide in all stories, and 16 feet 1 inch, 

 14 feet 4^ inches, and 10 feet 5 inches high in the first, second and 

 third stories, respectively. They have paneled jambs and heads. 

 The elevator openings in the southeast diagonal wall, two on each 

 landing, are 7 feet high and 3 feet wide. 



As in general plan so in detail a radical change occurs in the 

 fourth story from what may be called the typical finish of the stories 

 below. Pilasters 2 feet 10 inches wide and of relatively large 

 projection occupy corresponding positions to those in the lower 

 stories, but the 10-foot distance between each pilaster and the oppo- 

 site one across the corridor is spanned by a semicircular metal-furred 

 plaster arch instead of a fiat beam. These arches have a stilt of 6 

 inches above their bearing on the pilaster caps, the members of which 

 are continuous and 6 feet 4 inches high around all walls of the gal- 

 lery except where the screens occur. The spaces between the pilasters 

 on the diagonal walls are ceiled with low elliptical groined vaults, 

 while the larger spaces between the screens and the semicircular 

 clearstory windows have octagonal coffered barrel vaults over them. 

 On the southj due to the projection of the story over the portico, the 

 vaulted area is somewhat deeper than on the other sides. These 

 vaults are of 21 feet T inches radius, and like the rest of the fourth 

 story ceiling finish are applied to a false construction of metal 

 furring. 



The walls of the small triangular barrel-vaulted spaces at the in- 

 tersections of adjacent walls are pierced by 8-foot 9-inch by 5-foot 

 semicircular-headed door openings into the loft spaces of the east, 

 west and north wings and into two small rooms on the south. One 

 of these rooms, the eastern, is occupied bj'^ an iron stairway leading to 

 the space above the fourth story ceiling, from which access is had to 

 the elevator machinery and the dome. The elevator openings are 

 semicircular-headed and measure 8 feet 9 inches high by 3 feet wide. 



The radius of the clearstory windows, the exterior and general 

 features of which have already been described, is 19 feet 4 inches to 

 the inside line of a molded limestone archivolt, 17 inches wide and 

 consequently having a radius of 20 feet 9 inches, the same as that 

 of the great stone arches. A 9-inch band of these arches, exposed 

 around the coffered vaults, is recalled by a limestone band of simi- 

 lar depth around the window archivolts. The two mullions of the 

 windows have roseal marble paneled limestone faces on the interior, 

 3 feet 4 inches wide. 



Floor construction and finish. — ^The floor of the rotunda inside of 

 the piers and screens is supported by the Guastavino dome construc- 

 80120°— Bull. 80—13 4 



