SECRETARY’S REPORT 85 
Dr. Jacchia concludes that visual estimates of meteor brightness are 
strongly affected by the Purkinje effect when the meteors are fainter 
than magnitude —1. Such an effect is bound to influence all statistics 
and extrapolations based on visual meteor counts. 
In a study of the width of meteor trails, the Director and Dr. G. S. 
Hawkins found that the meteor columns had a finite diameter of 
approximately 1.3 m larger than would be expected from diffusion; 
the width is attributed to a continuous fragmentation process. 
Under the direction of Dr. John S. Rinehart, the Observatory has 
expanded its study of meteorites, as projected last year. Much has 
already been achieved toward the attainment of the four chief goals: 
Collecting and identifying micrometeorites in the upper atmosphere; 
designing and constructing an X-ray fluorescent microanalyzer, under 
the direction of Dr. F. Behn Riggs, Jr., to use for the point-to-point 
analysis of the metallic constituents of iron meteorites; measuring the 
abundance of isotopes in meteorites, under the direction of Dr. Edward 
L. Fireman; studying the surface features of meteorites for evidence 
of ablation. Dr. Rinehart has concentrated on the study of micro- 
meteorites and ablation. He and Paul Hodge designed a special col- 
lector, for use in aircraft, which filters and recovers particulate matter 
from the air. Some 30 high-altitude flights have now collected sev- 
eral thousand particles which are almost certainly of extraterrestrial 
origin. This program will expand during the next year. 
Edward P. Henderson of the U. S. National Museum and Prof. 
David Williams of the University of Florida have assisted in the 
detailed study of ablation; the surface features of the Grant Meteorite 
received particular attention. 
Studies of high-speed impact, in which meteoritic material was fired 
at bricklike materials, were initiated, and results of these tests are 
now being analyzed. 
Dr. Edward L. Fireman completed his investigation of the exposure 
time of meteorites to cosmic rays, and the energy of cosmic rays in 
space, by measuring the argon 39 in the Sikhote-Alin Meteorite. From 
measurement of this and other radioactive isotopes, he can estimate 
the probable age and original shape of various meteorites, and con- 
cludes that the Carbo Meteorite reached the earth about 1,500 years 
years ago, and was a nonspherical object in space. 
John Wood is attempting to relate the various types of silicate 
meteorites to a parent planet, and investigate the processes that take 
place during the early stages of planetary evolution. Carlos Var- 
savsky, as consultant to the Astrophysical Observatory, carried out 
calculations that indicate a lunar origin for tektites; he showed that 
the Whipple-Rinehart model for the ejection of tektites from the 
