66 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
and used as the site for an observatory. The reservation was in fact made, 
but no observatory has been established there. Mr. Abbot carried with him 
to Mount Whitney a pyrheliometer and wet and dry thermometers, and made 
observations on the summit both in the afternoon and morning hours. Both 
he and Mr. Campbell were favorably impressed with the advantages of the place 
for observing, and with the relative convenience of ascending the mountain, 
considering its great altitude. Fine building stone, sand, and water were found 
at the summit. Messrs. Campbell and Abbot, therefore, recommended to the 
Secretary of the Smithsonian Institution that a grant from the Hodgkins fund 
should be made for the purpose of erecting on the summit of Mount Whitney 
a stone and steel house to shelter observers who might apply to the Institution 
for the use of the house to promote investigations in any branch of science. 
This recommendation was approved, and the house is now in course of con- 
struction (July, 1909). 
It has been held by some astronomers that measurements of the “solar 
constant of radiation ”’ by high and low sun observations from a single station 
at a low altitude, or even at the altitude of Mount Wilson, are subject to a 
great error by reason of the impossibility of correctly allowing for loss in our 
atmosphere. In order to ascertain if this objection is well founded, an expe- 
dition to Mount Whitney by Mr. Abbot is planned for August, 1909. He will 
earry a complete spectro-bolometric outfit, for which Mr. Kramer has con- 
structed the mechanical parts in the shop of the Astrophysical Observatory at 
Washington. This apparatus will point directly at the sun, so as to dispense 
with reflections at a coelostat. A quartz prism and two magnalium mirrors 
constitute the sole optical parts of the spectroscope, as it will generally be 
used, but a glass prism and silvered mirrors will also be employed in the 
examination of the water vapor bands and of the infra-red spectrum. With 
the quartz and magnalium outfit it is expected to measure the energy of the 
spectrum from about wave-length 0.304 in the ultra-violet to wave-length 4y 
in the infra-red. Simultaneously with these “solar constant” measurements 
on Mount Whitney complete observations of the same kind will be made on 
Mount Wilson by Doctor Ingersoll, and if the results of the two shall agree it 
is thought that there will be left no ground for reasonable doubt of the accuracy 
of the method. 
SUMMARY. 
The principal work of the year comprises frequent spectro-bolometriec exam- 
inations of the relative brightness of different parts of the sun’s disk for rays of 
several different wave lengths; measurements of the transmission of long-wave 
rays, such as the earth emits, through very long columns of moist air; the 
steady continuation of the reduction of Mount Wilson and Washington observa- 
tions; six months of almost daily observation on Mount Wilson for the deter- 
mination of the variability of the sun; a preliminary observing expedition to the 
summit of Mount Whitney; and the complete preparation of apparatus and ar- 
rangements for a series of observations of the “ solar constant” by the spectro- 
bolometric method, to be me*e simultaneously at Mount Wilson and Mount 
Whitney in August, 1909. 
Respectfully submitted. 
C. G. ABBot, Director. 
Dr. CHARLES D. WALCOTT, 
Secretary of the Smithsonian Institution. 
