22 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



The equipment of the Zoological Park, both as regards the accom- 

 modations for the collections and facilities for visitors, is still in- 

 adequate and is inferior to that of other establishments of the kind 

 of equal importance. 



Many of the animals are kept in temporary quarters that are in- 

 sufficient in size, more or less insanitary, and quite costly to maintain. 

 This is particularly true of the fine series of birds, which includes 

 some of exceptional interest and rarity. The rough temporary build- 

 ing in which they are now kept is too small for the exhibition of the 

 entire collection and the conditions are such that it is difficult to keep 

 the birds in a good state of health. In a suitable structure the bird 

 collection would be one of the most attractive features of the park. 



Permanent paddocks are also needed for the hardy deer, wild 

 sheep, goats, and cattle, which are now scattered in temporary inclo- 

 sures, some of them altogether unsuitable. 



A new bridge across Rock Creek is urgently needed to replace the 

 present temporary log structure, and it should be of a permanent 

 character and sufficiently wide to provide for the greatly increased 

 travel when the valley of Rock Creek is fully developed. 



The roadways and walks in the park were greatly improved at the 

 cost of a special appropriation for that purpose. Nearly a mile of 

 the roads were treated either by reshaping and supplying a top layer 

 of stone or by regrading and furnishing the entire thickness of road- 

 bed metal. About If miles of walks were also laid or repaired and steps 

 were constructed where grades had before been too steep. A consid- 

 erable amount of work was also done to provide proper drainage. 



ASTROPHYSICAL OBSERVATORY. 



The Astroplvysical Observatory has been engaged in three principal 

 lines of work during the year. 



Observations by the spectrobolometric method were continued in 

 order to confirm the view referred to in last year's report that the 

 determinations of the intensity of the solar radiation outside the 

 earth's atmosphere are independent of the observer's altitude above 

 sea level, provided the conditions are otherwise good. Observations 

 for the " solar constant " were accordingly taken on Mount Whitney 

 in the summer of 1910, where opportunity was afforded also for 

 measurements of the brightness of the sky by day and by night, the 

 influence of the water vapor on the sun's spectrum, and the distribu- 

 tion of the sun's energy spectrum outside the atmosphere. The re- 

 sults of these observations show no discrepancy due to altitude be- 

 tween Mount Wilson (5,840 feet) and Mount Whitney (14,502 feet). 



It also seemed important to confirm by further observation the 

 variability of the solar constant of radiation. Observations were ac- 

 cordingly continued daily at Mount Wilson until November 10, 1910, 



