18 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946 
of sensitivity. Under the terms of a contract with the Office of the 
Quartermaster General, the Observatory is making a detailed study of 
sun and sky radiation at Camp Lee, Va., as part of the program to de- 
termine causes of tent-fabric deterioration. Eight copies of a special 
instrument based on the sensitive, quick-acting thermoelement devel- 
oped at the Observatory have been installed and put into operation at 
Camp Lee. A large volume of information is accumulating concern- 
ing the amount and kind of radiation, for each hour of each day, that 
falls on the tents being tested. Observations continued at the three 
field stations until February 1946, when the Tyrone, N. Mex., station 
was closed. The equipment will be installed temporarily at a sea-level 
location in Florida to study transmission of radiation through water 
vapor. Dr. Abbot published two papers dealing with his studies of 
the correlation between solar activity and weather changes. In the 
Division of Radiation and Organisms, experiments have been carried 
on in connection with improving the accuracy of apparatus used in 
determining the amount of carbon dioxide absorbed by green plants 
in the process of photosynthesis. The study of plant growth under 
controlled artificial conditions of mineral nutrition, illumination, tem- 
perature, and humidity has been continued. Further improvement 
of technique is being studied. 
PUBLICATIONS 
The Institution’s several series of publications constitute its chief 
means of carrying on the “diffusion of knowledge,” which joins with 
the “increase of knowledge” to form the purpose of the Institution as 
stipulated by the founder, James Smithson. The Smithsonian pub- 
lication program started in 1848 with one series, the Smithsonian Con- 
tributions to Knowledge, and as the Institution’s research work ex- 
panded over the years, other series were established to contain the 
several phases of its investigations until today the Smithsonian im- 
print appears on 14 distinct series. At the end of its first full century 
of existence, the Institution has issued some 7,500 individual publica- 
tions, of which 12,000,000 copies have been distributed. As the great 
majority of these works are the result of original researches, a large 
volume of basic new knowledge has been made available to the world 
through Smithsonian publications. It has been stated on numerous 
occasions that few textbooks or encyclopedias exist that have not drawn 
to some extent on publications of the Smithsonian Institution. 
Among the outstanding papers issued during the year may be men- 
tioned “A Bibliography and Short Biographical Sketch of William 
Healey Dall,” by Paul Bartsch, Harald Rehder, and Beulah E. Shields; 
“Sunspot Changes and Weather Changes,” by H. H. Clayton; “An 
