NATURAL HISTORY BUILDING 63 



and is pierced opposite the large windows with three large openings. 

 This construction is repeated in the second story, where the walls are 

 21^ inches thick and contain five openings. In this story, moreover, 

 the side walls of the light well also carry through to the above 

 described wall, each having a large opening. 



Besides the above, the only other walls of a subsidiary character 

 in these two stories are those of the light wells, the elevator shafts 

 and adjoining small rooms, and the stair wells, already referred to. 



Third story. — The width of the ranges, measuring 54 feet 2 inches 

 in the other stories, is in this story reduced to 51 feet 10 inches by 

 a furring of 3-inch terra cotta blocks built in front of the sloping 

 mansards in order to obtain straight vertical walls between the win- 

 dows, which are deeply recessed. This furring occupies a width of 

 13 feet If inches in each interspace between windows, and the spaces 

 enclosed by it contain the steel columns or struts supporting the outer 

 ends of the roof trusses. Additional terra cotta furring, 8 inches 

 thick, is built against the structural wall around the windows for the 

 purpose of giving greater outside reveal to the latter and of pro- 

 viding space in the jambs for the weight boxes. 



The typical plan of subdivision has been closely adhered to in the 

 third story except on the north side of the west wing, where the 

 entire space between the light well and the court wall has been left 

 undivided. The corridors extend through the middle of each range 

 and around three sides of each light well in the wings, the second 

 gallery in the rotunda furnishing passageway on the fourth side 

 and serving as a means of communication between the wings. The 

 corridors have a uniform width of 10 feet except at the north end of 

 the north wing and at the juncture of the ranges with the east and 

 west wings, where they are wider. The spaces between the corridors 

 and the outer and court walls vary in width from 19 feet 7 inches 

 to 22 feet 8|^ inches, except at the outer ends of the east and west 

 wings, where they are 37 feet 9^ inches wide, and at the northern end 

 of the north wing, where they are onlj'^ 16 feet 9^ inches wide. The 

 subdivisions or rooms formed by cross partitions in these window- 

 lighted spaces are generally of the dimensions of one and two units, 

 in two cases reaching three units and in a third four units. A few 

 exceptions occur, as in connection with the toilets and certain small 

 rooms used for closets and other purposes, and also at the outer ends 

 of the wings and the comers of the ranges, where the outer walls do 

 not entirely conform in measurement to the common unit. 



With the exception of the walls enclosing the rooms at the northern 

 end of the north wing, the toilet rooms and the stairs leading to the 

 lofts, which are of terra cotta, the partitions in the third story are 

 built of expanded metal or metal lath, embedded in cement mortar 

 and finished with plaster mortar to a thickness of 2 inches. The 



