14 
NATURE 
[Nov. 4, 1869 
THE RECENT TOTAL ECLIPSE OF THE SUN 
our American cousins in general hesitate to visit our 
9 
I little island, lest, as some of them have put it, they 
should fall over the edge ; those more astronomically in- | 
clined may very fairly decline, on the ground that it is a | 
spot where the sun steadily refuses to be eclipsed. ‘This | 
is the more tantalising, because the Americans have just 
observed their third eclipse this century, and already I 
have been invited to another, which will be visible in | 
Colorado, four days’ journey from Boston (I suppose I | 
am right in reckoning from Boston ?) on July 29, 1878. 
Thanks to the accounts in Sz/iman’s Fournal and | 
the Philosophical Magazine, and to the kindness of 
Professors Winlock and Morton, who have sent me some 
exquisite photographs, I have a sufficient idea of the 
observations of this third eclipse, which happened on the 
7th of August last, to make me anxious to know very much 
more about them—an idea sufficient also, I think, to 
justify some remarks here on what we already know. ; 
A few words are necessary to show the work that had 
to be done. 
An eclipse of the sun, so beautiful and yet so terrible to 
the mass of mankind, is of especial value to the astronomer, 
because at such times the dark body of the moon, far out- 
side our atmosphere, cuts off the sun’s light from it, and 
round the place occupied by the moon and moon-eclipsed | 
sun there is therefore none of the glare which we usually 
see—a glare caused by the reflection of the sun’s light by 
Violet end. 
CL 
g sea : “¥ 
hydrogen: hydrogen=: = hydrogen 
=Fs2 2 Geli s HES 
the sun was eclipsed, and did not travel with the moon— 
that the red prominences really do belong to the sun. 
The evidence, with regard to the corona, was not quite 
so clear; but I do not think I shall be contradicted when I 
say, that prior to the Indian eclipse last year the general 
notion was that the corona was nothing more nor less 
than the atmosphere of the sun, and that the prominences 
were things floating in that atmosphere. 
While astronomers had thus been slowly feeling their 
way, the labours of Wollaston, Herschel, Fox Talbot, 
Wheatstone, Kirchhoff, and Bunsen, were providing them 
with an instrument of tremendous power, which was to 
expand their knowledge with a suddenness almost startling, 
and give them previously undreamt-of powers of research. 
I allude to the spectroscope, which was first successfully 
used to examine the red flames during the eclipse of last 
year. That the red flames were composed of hydrogen, 
and that the spectroscope enabled us to study them day 
by day, were facts acquired to science independently by 
two observers many thousand miles apart. 
The red flames were “settled,” then, to a certain 
extent ; but what about the corona? 
After I had been at work for some time on the new 
method of observing the red flames, and after Dr. Frank- 
land and myself had very carefully studied the hydrogen 
spectrum under previously untried conditions, we came to 
the conclusion that the spectroscopic evidence brought 
forward, both in the observatory and in the laboratory, was 
against any such extensive atmosphere as the corona had 
Red end. 
CNB. 
= hydrogen 
D 
: Pah 
sodium 
1.—Showing the solar spectrum, with the principal Fraunhofer lines, and above it the bright-line spectrum of a prominence containing 
magnesium, sodium, and iron vapour at its base. 
our atmosphere. If, then, there were anything surrounding | 
the sun ordinarily hidden from us by this glare, we ought 
to see it during eclipses. 
In point of fact, strange things are seen. There is a 
strange halo of pearly light visible, called the corona, and 
there are strange red things, which have been called red 
ames or red prominences, visible nearer the edge of the | 
moon—or of the sun which lies behind it. 
Now, although we might, as I have pointed out, have 
these things revealed to us during eclipses if they be- 
longed to the sun, it does not follow that they belong to 
the sun because we see them. Halley, a century and a 
half ago, was, I believe, the first person to insist that 
they were appearances due to the moon’s atmosphere, 
and it only within the decade that modern 
science has shown to everybody’s satisfaction—by photo- 
graphing them, and showing that they were eclipsed as 
is last 
| Stronger and stronger ; but there was alway 
been imagined to indicate ; and we communicated our 
conclusion to the Royal Society. Since that time, I con- 
fess, the conviction that the corona is nothing else than an 
effect due to the passage of sunlight through our own 
atmosphere near the moon’s place has been growing 
s this consider- 
ation to be borne in mind, namely, that as the spectro- 
scopic evidence depends mainly upon the brilliancy of the 
lines, that evidence was in a certain sense negative only, 
as the glare might defeat the spectroscope with an un- 
eclipsed sun in the coronal regions, where the temperature 
and pressure are lower than in the red-flame region. 
The great point to be settled then,'in America, was, 
What is the corona? and there were many less ones. For 
instance, by sweeping round the sun with the spectroscope, 
both before and after the eclipse, and observing the pro- 
minences with the telescope merely during the eclipse, we 
