NATURAL HISTOEY BUILDING 93 



flues, however, like those starting in the ground story of the middle 

 wing and the ranges, have an inconsiderable influence on the ventila- 

 tion of these stories, for which it was deemed unnecessary to intro- 

 duce an elaborate mechanical system. Both stories are of consider- 

 able height, and circulation in each of them is unobstructed around 

 the entire building, the few intersecting walls being pierced with 

 especially large openings. The two stories also communicate with 

 each other through the openings in the light wells, and with the 

 rotunda, and have the advantage of the elevator shafts and stair 

 wells leading to the third story and the attics. All of the windows 

 are provided with hinged panes through which air can be directly 

 admitted. The effect of the heat from the radiators placed under 

 or against the great window surfaces is to maintain an active circula- 

 tion in cold weather, and, judging from the experience so far gained, 

 there is no reason to suppose that the exhibition halls will ever be- 

 come uncomfortable or unwholesome from lack of ventilation. The 

 air contents of the first story amount to about 2,166,000 cubic feet, 

 and of the second story^ to about 1,591,000' cubic feet, a liberal al- 

 lowance for even the largest attendance of visitors that may be ex- 

 pected at any time. 



The third story, however, calls for effective ventilating measures, 

 in view of its proximity to the roofs, its relatively small rooms, the 

 extensive collections in storage and the number of persons who work 

 there. The numerous windows, hung with double sashes, can be 

 opened to admit air either from the top or bottom. Above each of 

 the entrance doors, which are opposite the windows, is a grated open- 

 ing. The natural drift of the air in the corridors is toward thf3 

 elevator shafts and stairways, and in the wings the hinged panes in 

 the transoms along the upper part of the light well walls afford 

 means for direct communication with the exhaust chambers. For 

 mechanically withdraAving the air there is a flue in each alternate 

 pier chase and a ceiling register opening in front of each window, 

 or two ducts in every unit length of 18i feet on both sides of the 

 wings and ranges, all of which lead into the attic spaces in the man- 

 ner before described. 



Auditorium and rotunda. — Owing to the doubly enclosed position 

 of the auditorium in the ground story of the south pavilion, it has 

 been necessary to provide for its ventilation through the medium of 

 a special system, in which the rotunda also participates. The air is 

 drawn into the building through a window by means of a full-housed 

 fan of the American Blower Company's make, operated by a 12 

 horse power Dielil motor and installed in a small room adjoining 

 the entrance imderneath the south portico. Before reaching tlie 

 fan, however, it passes first through a cast-iron Utica pin radiator 

 of the hot water type, next through an air washer, and finally through 



