SECRETARY'S REPORT 1433 
born or hatched at the Zoo was 157—56 mammals, 62 birds, and 39 
reptiles. Personne! recruitment and training for the organization 
progressed satisfactorily, and the most needed repairs and minor im- 
provements to buildings and grounds were carried out. The year’s 
total of visitors to the Zoo was the largest ever recorded—3,346,050, 
an increase of more than 300,000 over the previous year. Groups 
from schools, some as far away as Maine, Florida, Texas, and Cali- 
fornia, numbered 1,844, aggregating 93,632 individuals. 
Astrophysical Observatory —Year-long tests at the three most 
promising sites for a new high-altitude solar observing station indicate 
that the best skies prevail at the Clark Mountain, Calif., site, the 
second-best site being Pohakuola, Hawaii. Estimates of the cost of 
establishing a field station on Clark Mountain, however, proved to be 
in excess of available funds, forcing postponement of building opera- 
tions. Data and tables were prepared which simplify computations 
at the field observing stations by eliminating the tedious curve-plotting 
process heretofore used in obtaining the air mass. Daily observations 
of the solar constant of radiation were continued at the Montezuma, 
Chile, and Table Mountain, Calif., stations. Intercomparisons 
between the substandard silver-disk pyrheliometer S. I. No. 5 and the 
instruments in use at Miami, Montezuma, and Table Mountain show 
no material changes in constants, confirming the adopted scale of 
pyrheliometry. Special radiation measurements started in 1945 at 
Camp Lee, Va., under contract with the Office of the Quartermaster 
General, were continued there, half of the year by the Observatory 
and half by the Quartermaster Board; similar measurements were also 
made at Miami, Fla., and at Montezuma, Chile. The work of the 
Division of Radiation and Organisms has been concerned chiefly with 
reorganizing and reequipping the laboratories. Besides new office 
space which has been established, five rooms are being converted into 
constant-condition rooms for biological experimentation, and four 
chemistry laboratories will be available. In addition, a photographic 
laboratory, an X-ray room, a cytology laboratory, an electronics 
laboratory, and two general laboratories are being arranged. 
National Air Museum.—The Air Museum was given the responsi- 
bility of receiving, bringing to Washington, and preparing for exhibi- 
tion the original Wright Brothers aeroplane of 1903, presented to the 
National Museum in December 1948. A storage depot to be used by 
the Air Museum until it has a building of its own was acquired in 
November 1948 in the former Douglas Aircraft plant at Park Ridge, 
Ill. There a field organization was installed, and the Air Museum 
assumed custody of the storage facility itself and the large collection 
of planes and other aeronautical material stored there by the U. S. 
Air Force for the Museum. The Advisory Board held three meetings 
