18 EEPORT OF NATIONAL, MUSEUM, 1922. 



BUILDINGS AND EQUIPMENT. 



Shortly after the completion of the Natural Historj^ Building, it 

 was noted that the keystone in the east arch of the rotunda was 

 slightly out of place. As years passed the same thing occurred, in 

 lesser degree, in the west arch, and a slight separation appeared in 

 the joints of the balustrade on the fourth story, just below the stone 

 arches. These joints were plastered up from time to time, but, owing 

 to the inaccessibility of the keystones, no steps were taken either to 

 put them back in place or to fill the exposed openings. The condition 

 of these keystones, although not considered dangerous, distinctly 

 marred the appearance of the rotunda. The location of the east 

 keystone continued to change, however, and it was deemed advisable 

 this year to have a thorough investigation made. As the result of 

 two examinations of the dome and the great piers supporting the 

 dome, it was found that the displacement of the stone arches which 

 span the piers, the opening of joints at the ends of the balustrades 

 xmder these arches, and in the fourth story floor at the ends of the 

 piers have all been brought about by a movement at the end of the 

 piers in a direction away from the center of the rotunda. As there is 

 no indication of movement of the piers in the lower portion of the 

 building, it appears that they have simply leaned outward at the 

 top, doubtless caused by the eccentric application of the weight of 

 the dome. Since the piers are fully braced by a large number of steel 

 beams to the walls of the building and no movement of the outer 

 walls has been observed, it is assumed that the walls are successfully 

 resisting the pressure from the piers and that the movement of the 

 latter will probably not continue much farther, if at all. In the 

 meantime an ingenious method of measuring the exact location of the 

 keystones has been devised, and careful observations will be made at 

 intervals of a few months to determine what, if any, further dis- 

 placement occurs. 



Aside from the usual upkeep, the more important repair work 

 this year in the Natural History Building consisted in the painting 

 of ceilings, side walls, and steel roof trusses in the space between 

 the inner skylights and the roofs of the three main halls; painting 

 all borders in corridors on ground and third story; plastering and 

 pointing up the walls all over the buildings ; repainting floors in the 

 two west ranges, ground story, with wood preservative paint; com- 

 pleting and varnishing the cork flooring in the corridors at the east 

 end of the east hall, third story, and painting adjacent floors; in- 

 stalling ventilating ducts and painting ceilings, walls, and floors in 

 four housekeeping rooms; changing ventilating ducts in the engine 

 room; renovating and repainting large doors at the east and west 

 or service entrances ; and the painting of all exterior wooden window 



