MODERN THEORIES OF THE SUN——BOSLER. 159 
It seems extremely probable therefore that the solar matter is 
electrified. The radiation pressure which, as Maxwell demonstrated 
and experiment confirmed, is exercised upon any body struck by 
light, helps in the expulsion of the charged particles. The wings and 
filaments of the corona are doubtless due to this force which also 
explains the tails of comets. They are probably real cathode rays 
which the least magnetic field will deviate (M. Deslandres) and which 
volute around the lines of force. The corona thus gives us an image 
of the general magnetic field of the sun analogous to the terrestrial 
magnetic field (a sphere uniformly magnetized) and also similar 
to that of a rotating sphere electrically charged (pl. 1, figs. 1, 2). 
Along another line of reasoning, the interpretation of the prominences 
has shared in these new notions. It has been thought strange that 
a gas should have ve- 
locities of upwards of 
a hundred kilometers a ; ! 
second. But in an ion- ; 
ized gas only an infini- i notosphep, 
tesimal number of the ; 
molecules participate in , 
sending out the light : 
(Perot). These few may { 
alone have the enor- 
mous velocities within 
a gas itself almost immobile, just as is the case of the canal rays of 
a Crookes’ tube. 
A brilliant discovery in America in 1908 throws further light on all 
these theories. Hale, by means of the Zeeman phenomenon, has 
shown, within the nuclei of sun spots, magnetic fields of 3,000 or 4,000 
Gausses, roughly normal to the surface and explaining perfectly 
the enlargements and doublings of the corresponding lines in the 
spectrum. Indeed, these magnetic fields seem to be vortices of 
electrified matter: the ionization would have to be no more intense 
than that observed in the laboratory either in vacuum tubes or in the 
neighborhood of hot bodies. 
Connected with this same line of thought is the study of the radial 
velocities in the various chromospheric layers. This has permitted 
Deslandres, Evershed, and St. John to investigate the phenomena 
occurring in sun spots. Above the penumbra, the absorbing vapors 
spread out from the center of the spot parallel to the surface; arriving 
at the peripheral facula, they rise, come back higher toward the center 
(fig. 5) and are finally engulfed within the cavity (nucleus) of the spot 
where other researches have shown relatively low temperatures. 
As in the case of eddies in rivers, the cause of this suction may be 
looked for in the subjacent whirlpools, the very ones which probably 
; Penumbra Nucleus )Fenumbra 1 
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Fia. 5. 
