26 
NATURE 
[Nov. 10, 1870 

This passage induced me to submit to the trial and judgment 
of my fellow-members of the Physical section of the Royal Academy 
a very simple hypothesis regarding the nature of the Corona, 
which entered my mind shortly after the observation of the total 
eclipse of August 18, 1868.* 
1 think—and, if I am not mistaken, all astronomers agree with 
me—that a part of the luminous phenomenon which we call the 
Corona belongs to an atmosphere of the sun,+ having a feeble 
reflecting power, or being itself luminous. But the beams in the 
Corona, whose variability is now confirmed anew, are necessarily 
an optical phenomenon, They originate, I believe, in the in- 
equalities of the moon’s surface. Ifthe sunlight slants somewhere 
along the moon’s limb through a va//ey, we observe from our 
point of view a Jeam, provided there exist between the moon 
and us particles able to reflect the sunlight, or to transmit it like 
semi-transparent bodies. There is no need to have recourse to 
diffraction. 
To look for these particles in the atmosphere ot the earth, 
as Mr. Gould does, is, in my opinion, not tenable, as the Corona 
and the beams have also been observed in eclipses, where the 
cone of the shadow even had} a breadth of thirty-six German 
leagues. The molecules of the atmosphere, which we see around 
the eclipsed sun, are wholly within the cone of the shadow. 
These reflecting particles are undoubtedly to be looked for 
beyond our atmosphere, between the moon and the earth, and 
I believe that they may be regarded as identical with those | 
particles which float in the ether, and under other circumstances 
cause the zodiacal light. 
That the zodiacal light, or rather the particles which cause it, 
reach the earth’s orbit, is, as regards nearly its whole circumference, 
not subject to any doubt, as the apex of the zodiacal light is ““ mostly 
farther off the sun than 90°. Only in the months of March and 
April is it not possible to follow the zodiacal light so far” 
(Schmidt, ‘‘ Das Zodiacallicht,” Braunschweig, 1856). But then, 
at those particles which are situated on the apex of the zodiacal 
light, the sun’s ray makes a right angle with the line which joins 
the earth, and the circumstances are not favourable for small and 
widely-dispersed particles to reflect much sunlight in the direction 
of the earth. It is, therefore, probable that in March and April 
these particles would show themselves farther from the sun 
if the illumination were stronger. At a total eclipse of the sun 
that angle is 179}° for a particle visible at 30’ distance from the 
moon’s limb, and 179%° for particles in the immediate neighbour- 
hood of the moon’s limb; and it is an acknowledged fact that, | 
ander these circumstances, there is much more light reflected than 
‘if reflected at a right angle. Moreover, the intensity of the trans- 
mitted light increases equally with this angle. 
Schmidt mentions, in his above-quoted work, that he and other 
observers, during the total eclipse of July 28, 1857, looked 
out for the zodiacal light, but in vain. He thought the sky 
not dark enough, and expresses himself as follows :—‘‘ Das 
Ansehen der den schwarzen Mond umgebenden vielstrahligen 
Corona war im ganzen betrachtet nicht gerade geeignet, sie 
sogleich in Beziehung zum Zodiacallichte zu denken.” 
Thus it seems that the beams made Schmidt conclude, ‘* This 
is no zodiacal light.” If my explanation is the true one, and if 
the sun’s atmosphere is accepted as unlimited, and gradually pass- 
ing over into the ether, then the light of the Corona, which equally 
surrounds the moon, falls altogether into the same category as the 
beams, only that it originates in the reflecting particles beyond 
the moon. Accordingly, my hypothesis is expressed thus : Both 
the Corona and its beams have the same origin as the zodiacal light. 
I remark, finally, that the strangely curved form of some beams, 
as well as their variability, may be very well accounted for on 
this hypothesis—the curved form by the irregularity of the moon’s 
surface. For instance: I take a particle of light of a beam of 
the Corona ; I imagine myself in the molecule which, according 
to my hypothesis, corresponds with that pariic'e of light, and 
which is situated between the moon and my eye. Looking, then, 
from that stand-point to the moon, I must see the light of the 
sun slanting over a valley; but if I move myself laterally—ée. 
in the direction parallel to the moon’s radius which corresponds 
with that valley—then it is not certain that I shall see on the 
samé point an extraordinary amount of light, for it is possible 
that at the same place a ridge has intervened. It is, however, 
* At the Island of Mantawalu-kéké (near Celebes), where I had the 
pleasure of meeting the Commander (Captain Bullock) and the Etat-Major 
of H.M.S. Serpent, and the Spanish astronomers of the municipal Athe- 
nzum at Manilla, the fathers Faum, Nonnell, and Ricardo. 
+ This is probably the Chromosphere, as seen in the Eclipse,—Ep, 
t (Sudinteliige); at the surface of the earth, 1 


very possible that, if i move in a direction perpendicular to the 
former (and also perpendicular to the direction towards the earth), 
Icome into a region where that ridge does not intervene, but 
where the continuation of the valley is again visible, through 
which the sunlight slants. In this case, the beam of the Corona— 
z.é. the effect produced by those particles which receive more 
light than others at equal distances from the surface of the cone, 
having its apex in the eye, and which surrounds the moon—has 
a curved form. 
The variability is, I think, satisfactorily explained by the 
motion of the moon passing by the sun, : 
This hypothesis forced itself upon me when at Toli-holi* I saw 
the moon rising behind a hill. Before she made her appearance 
her light shone over the trees, and produced, in a hazy air on my 
side of the hill, beams which very much resembled those of the 
Corona. I do not know whether the zodiacal light has already 
been analysed by the spectroscope ; if so, the comparison of the — 
spectra of zodiacal light and the Corona will serve to test my 
hypothesis. ; 
A second test is this: total eclipses observed in the months 
of December and January should show less brilliant beams than 
total eclipses observed in other months, since in December and 
January the earth is near the direction of the perihelion of the 
circumference of the zodiacal light. The next total eclipse of 
December 12, 1871, will perhaps give some information on this 
point. + J. A. C. OUDEMANS 
Batavia, Sept. 2 

The Fuel of the Sun 
In your impression of October 6 Mr. Murphy adds another 
to the frequent attempts that are still made to galvanise the 
expiring hypothesis that attributes the solar heat and light to 4 
meteoric bombardment. Many very strong and sufficient ob- 
jections have been already brought against it, but as Mr. Murphy 
states that he is *‘ not mathematician enough to form any opinion 
on the merits of the controversy,” I will add two arguments 
which to my mind are quite sufficient to annihilate this expla- 
nation—both of which may be sufficiently understood without 
mathematics, and neither of which have I ever seen fairly 
stated. 
1st. The advocates of the meteoric bombardment usually start 
from the fact that great meteoric showers fall upon the earth. 
Thus, Dr. Tyndall, in his lectures on ‘‘ Heat considered as a 
Mode of Motion,” introduces Mayer’s hypotheses, with an 
account of the number of meteors counted during the August 
and November showers ; and these observed meteors and a few 
comets are the only actual observed material upon which this 
bombardment theory rests—all beyond them are mere fignients 
of mathematical imagination, and any supplies derived from the 
zodiacal light, or otherwise exclusively from the space within the 
earth’s orbit, must have been exhausted within the period of 
human existence. 
Now, it is quite obvious, without any detailed calculation, that 
if these meteoric bodies, coming from anywhere you please out- 
side of the earth’s orbit in sufficient quantities to maintain the 
heat and light of the sun, had fallen, as they must have done, 
upon the earth in a proportion due to its magnitude and position, 
they must in the course of a few millions of years—say from the 
era of the Laurentian rocks to that of the London sewage 
deposits—have covered the earth with a very important super- 
ficial stratum, instead of merely supplying a few rare specimens 
for our museums. Every slowly deposited sedimentary tock 
upon the face of the earth should be thickly peppered and con- 
glomerated with meteoric dust and nodules. With these con- 
siderations and the well-known geological facts before us, I 
need scarcely state the obvious conclusion, viz. that the evidenees 
in support of the theoretical terrestrial requirements of this 
bombardment hypothesis are contemptibly insufficient. 
My second objection attacks the fundamental basis of this 
hypothesis, and I think destroys it altogether. I maintain that 
any explanation of the sources of solar light and heat which does - 
not equally and necessarily account for the radiations of all the 
other self-luminous orbs that people the whole immeasurable 
depths of space, is philosophically worthless. It is thus worth- 
less if it does not also account for the perpetual renewal, the 
constancy, the eternal permanence, of all these radiations, The 
pale nebule, as well as the brighter suns, should be equally 
included in its grasp. 
* Vuilgo, erroneously, Tontoli, north eoast of Celebes: 
t We hope also something from next month’s eclipse.—Ep. 

