ASTRONOMY: ADAMS AND BURWELL 
127 
gives a corresponding value of 100 volts per centimeter. It therefore 
seems safe to say that the electric iield-strength at the level in question 
is less than 200 volts per centimeter."^ 
Salet and Millochau, using lower dispersion, had previously found a 
maximum value of 7000 volts per centimeter for Ey in the chromo- 
sphere.^ Our much lower value indicates that in order of magnitude 
the electrical potential differences in the solar atmosphere may not 
greatly exceed those in the lower atmosphere of the earth, where they 
average about 1 volt per centimeter. In thunderstorms, of course, 
enormously greater differences occur, and it remains to be seen whether 
appreciable electric fields can be detected in solar eruptions, where the 
conditions for their production appear to be more favorable than in the 
quiet regions of the atmosphere. 
^ For a summary of the views of Goldstein, Bigelow, Deslandres, Arrhenius, and others 
on the electrical condition of the solar atmosphere see B osier, Les theories modern du soleil; 
also recent papers in the Comptes Rendus Paris Acad. Sci. 
^ See Stark, Elektrische Spectralanalyse chemischer Atome, Hirzel, Leipzig, 1914. 
2 Hale, Solar Magnetic Phenomena, Proc. Amer. Phil. Soc, April 24, 1914, p. 254. 
■* Under high dispersion. Stark has resolved into many components (loc. cit., Plate 
III). A variation in the relative intensities of these components under solar conditions, 
which is not improbable, might introduce an error into a determination of the maximum 
intensity of the electric field. It is likely, however, that the results here given are of the 
true order of magnitude. 
^ Salet and Millochau, C. R. Paris Acad. Sci., 158, 1000 (1914). 
RESULTS OF AN INVESTIGATION OF THE FLASH SPECTRUM 
WITHOUT AN ECLIPSE 
REGION X 4800 TO X 6600 
By Walter S. Adams and Cora G. Burwell 
MOUNT WILSON SOLAR OBSERVATORY, CARNEGIE INSTITUTION OF WASHINGTON 
Presented to the Academy, J6inuary 18, 1915 
The study of the bright line spectrum given by the comparatively 
thin layer of gases which constitutes the sun's atmosphere has usually 
been limited to the brief periods of total solar eclipses. During the 
few minutes that the dark body of the moon covers the sun's image the 
spectrum of the shell of radiating gases surrounding the sun may be 
observed without difficulty, and photographs of this spectrum, known to 
astronomers as the spectrum of the flash, have formed one of the most 
important products of recent eclipse expeditions. 
Although admirable results have been secured in this way the 
