NATURAL HISTORY BUILDING 59 



The ceiling lights are identical in design and construction in the 

 three wells. The glass area, which is of the same width in all, 

 namely, 29 feet 3^ inches, is 147 feet 4 inches long in the east and 

 west wings and 147 feet 11^ inches long in the north wing. All are 

 composed of panels of |-inch wired plate glass, longitudinally ribbed 

 on the under surface, measuring 1 foot 5^ inches by 5 feet 5^ inches 

 and set in T-shaped wrought iron sash bars. The primary framing 

 of the lights as a whole consists of 15-inch channels around the outer 

 edge, and of 8-inch I beams running transversely and longitudinally 

 across and along the lights. These give attachment to a framework 

 of light steel bars supporting the sash bars, and the entire framework 

 is suspended from the roof trusses of the skylights. The longitu- 

 dinal beams are embedded in the plaster work of beams which project 

 slightly from the under side of the light, and separate the central 

 portion of the light from glazed border bands, 4 feet 4 inches wide, 

 along the sides. The transverse beams occur above the longitudinal 

 ones and have suspended from them plaster beams similar to the 

 above, forming dividing lines across the light at intervals of 18 feet 

 G inches. The ceiling lights are reached from the upper side by 

 means of wood walks for cleaning and repair. 



SUBDIVISION OF THE STORIES 



Plan of suhdivision. — The ground and third stories have been 

 extensively subdivided into compartments for laboratories, the 

 storage of specimens, shops, offices, etc., and some simple partitions 

 have been built in the lofts, but in the first and second stories the 

 principal constructions of a subsidiary nature besides those enclosing 

 the light wells are certain screen walls introduced to subserve the 

 purposes of public installation. The enclosures of the elevator 

 shafts and stair wells in the north wing and the ranges, however, are 

 all built to a gi'eater or less extent of terra cotta, though in all cases 

 but one they are partly bounded by structural walls, the same condi- 

 tions being repeated in all stories, and in the first and second stories 

 terra cotta screens enclose the space between the stair well and the 

 elevators in the north pavilion. 



The subdivision of the ground and third stories has been based 

 upon a uniform plan, which comprehends the utilization of nearly all 

 the window lighted space for working purposes and consequently the 

 placing of the corridors as far as possible or as far as was expedient 

 from the outer and court walls. The typical arrangement contem- 

 plated a corridor through the middle of each range and one around 

 the middle part of each wing, adjoining the light wells in the third 

 story and the dark area occupied by the piers in the ground story. 

 While the typical plan has been carried out with little deviation in 



