SECRETARY’S REPORT 11 
the three sites for extended tests to determine which is the most satis- 
factory. A redetermination of the Smithsonian standard scale of 
solar radiation confirmed the Observatory’s belief that the scale of a 
silver-disk pyrheliometer will remain unchanged for many years. 
Research projects completed or well advanced during the year in 
the Division of Radiation and Organism included studies of the res- 
piration of broad-leaf plants; investigations on the effects of environ- 
mental factors on the germination of seeds; and studies of the 
developmental physiology of grass seedlings. 
The results of Observatory research appeared in nine papers pub- 
lished during the year. 
National Air Museum.—Created as a bureau of the Smithsonian 
Institution in 1946, the National Air Museum did not begin actual 
operations in its own right until August 1, 1948, when its first appro- 
priation of $50,000 became available. Thereupon the Institution’s 
aeronautical collections and staff were transferred to the Air Museum, 
the staff was increased from two to seven persons, and separate offices 
were provided in the Arts and Industries Building of the National 
Museum. The Air Museum’s Advisory Board met twice during the 
year and made two important decisions: 1, that there be used as a 
storage depot for the temporary safekeeping of Air Museum material 
a part of the Douglas aircraft plant built during World War II on the 
outskirts of Park Ridge, Ill., 20 miles from Chicago; and 2, that the 
Air Museum should be located in the Washington area and that the 
aid of the Public Buildings Administration be enlisted in designing 
an adequate air museum building. The Public Buildings Adminis- 
tration later in the year submitted a preliminary plan for a building 
which was approved by the Board. Numerous improvements were 
made to the present exhibits in the Aircraft Building, and several 
special exhibits were prepared during the year. A large part of the 
time of the curatorial staff was devoted to surveys to determine what 
items should be added to the aeronautical collections and what ma- 
terial was available throughout the country. <A total of 330 objects 
were acquired during the year, the largest number of aeronautical 
acquisitions recorded in any year of the Smithsonian’s history. 
Canal Zone Biological Area.—This tropical laboratory on Barro 
Colorado Island, placed under Smithsonian administration in 1946, 
celebrated its twenty-fifth anniversary on April 17, 1948, and in honor 
of the occasion the Canal Zone issued a special commemorative 10-cent 
stamp. The island is maintained as a completely unspoiled tropical 
forest area, with laboratory facilities for investigations in biology 
and related subjects. Some 20 scientists from numerous universities 
and institutions came to the island to carry on investigations in widely 
varied fields, including army-ant studies, a survey of the fresh-water 
fishes, termite control through soil poisoning and wood treatment, the 
