124 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1948 
In September, while vacationing in Honolulu, the Director learned 
of a site on the island of Hawaii where the annual rainfall is less than 
10 inches and the skies described as remarkably clear. He visited that 
location where, at an altitude of 6,500 ft., he found a road, abundant 
water supply, electric power and telephone already installed, and skies 
which may prove to be clear and uniform from day to day. 
In October Dr. Abbot and A. F. Moore visited the region of southern 
California near the Nevada border, including Clark Mountain (7,900 
ft.), where the annual precipitation is 8 inches. They encountered 
excellent skies in this region. 
Since tests covering an extended period are the only safe criteria 
for determining a satisfactory site for a solar station, Mr. Hoover in 
May 1948 installed a recording Eppley pyrheliometer at each of the 
three following promising sites: (1) Torreon, Coahuila, Mexico; (2) 
Mountain Pass, Calif., near Clark Mountain; and (3) Pohakuola, 
Island of Hawaii. The instruments are operated through the kind 
cooperation of men living near the sites. The records for the month 
of June 1948 indicate Clark Mountain as having the best skies thus far. 
Dr. Abbot and the Director spent a month beginning August 10, 
1947, at the Mount Wilson Observatory, Calif., having planned to 
assist each other on two projects. One project was to redetermine the 
Smithsonian standard scale of solar radiation. We reconditioned, 
remounted, and adjusted our standard double water-flow pyrheli- 
ometer, last used in 1934, and made a series of careful comparisons 
between it and two substandard silver-disk pyrheliometers which we 
had carried by hand from Washington. The mean of 83 comparisons 
agrees within 1 part in 1,000 with the results of 1934 and 1932. This 
confirms our belief that the scale of an individual silver-disk pyrheli- 
ometer with ordinary care will remain unchanged over a long period 
of years. 
The second project was a continuation of Dr. Abbot’s previous work 
to determine the energy spectra of some of the brighter stars, with the 
aid of the 100-inch Mount Wilson telescope. Dr. Abbot’s sensitive 
radiometer, now under excellent control, permitted actual measure- 
ments on eight different stars at eight different wave lengths. Since 
the percentage accidental error was rather large, only the general 
forms of these curves were determined. Dr. Abbot has encouraging 
plans for improvement in the measurements and he hopes to repeat 
this project in the near future. 
(2) DIVISION OF RADIATION AND ORGANISMS 
Owing to the illness and death of the chief of the division, Dr. Earl 
S. Johnston, and to changes in personnel, the research program in 
progress at the beginning of the year was necessarily altered and 
somewhat curtailed. Leonard Price, now the senior staff member of 
