48 
POPULAE SCIENCE EEYIEW. 
second, the shifting lights around the horizon, as the shadow 
sweeps across the station of the observer, would tend greatly to 
encourage the illusion. To this may be added the circumstance 
that at the first formation of the corona, and as it is disappear- 
ing, an apparent rotational movement results from the rapid 
closing in and separation of the solar cusps. I find that the 
accounts of apparent motion in the coronal beams are few in 
number and of little weight compared with those which assert 
the fixity of the rays ; and I cannot recall any instance in which 
an observer speaks of the apparent motion as of a phenomenon 
he had been at the pains to convince himself of, whereas those 
who refer to the fixity of the beams speak sometimes very 
definitely on this point. 
Here are a few accounts of apparent motion. 
Hon Antonio d’Ulloa, speaking of the eclipse of 1778, says, 
“ the corona seemed to be endued with a rapid rotatory motion, 
which caused it to resemble a firework turning round its 
centre.” But it does not seem at all clear that he refers to 
the beams, because he says, “ there appeared issuing from the 
corona a great number of rays of unequal length, which could 
be discerned to a distance equal to the lunar diameter.” This 
“ discerning ” of the rays seems to imply that they were un- 
moved ; and certainly the observation would prove too much 
if it were accepted as establishing a sort of Catherine-wheel 
motion of the radial beams. 
In 1842 several observers, says Grrant, “asserted that the 
ring of light ” (not the rays) “ turned continually round its 
centre.” “ At Lipetsk,” he adds, “ the light of the ring seemed 
to M. Otto Struve to be in a state of violent agitation.” Then 
follows the best testimony yet given in favour of apparent 
changes in the beams. “Mr. Baily states,” says Professor 
Grrant, “ that the rays had a flickering appearance, somewhat 
like that which a gas-illumination might be supposed to assume 
if formed into a similar shape.” It will be admitted, however, 
that there is here no convincing evidence of a change of place 
in the beams, and further that the changes of brightness are 
fairly comparable with those flickerings which Chladni, Encke, 
Humboldt, Bessel, and other astronomers have noted in the 
case of comets, and which have even at times been noticed in 
the zodiacal light. When we remember that the coronal beams 
are necessarily seen through our atmosphere, which must 
undergo very important changes of temperature during the 
continuance of totality, and probably be subject to waves of 
disturbance, we cannot wonder that the illumination of these 
delicate objects should seem fitful. 
How when we turn to narratives describing the fixity of the 
coronal beams, we find much more satisfactory evidence. 
