498 
NATURE 
[ Sept. 23, 1886 
facts have been acquired, old views have been satisfactorily 
tested, new instrumental methods have been studied, and 
records of the general phenomena have been secured. 
I will as briefly as possible go over each of these points 
in turn. 
“ First as to the new facts. For these we have to refer 
to the work of Prof. Tacchini at Boulogne. No one was 
more competent than he to note the prominences and other 
appearances visible during the eclipse. This he did with 
a 6-inch, and so soon as the clouds permitted after the 
eclipse he observed the spectrum of the prominences by 
the ordinary method. 
seen under these two different conditions and by means 
of such different methods were not the same. He also 
noted that the prominences seen during the eclipse itself 
had the same characters as the so-called ‘white’ pro- 
minences which he observed in 1883 at the Caroline 
Islands. These appear whiter and dimmer as the dis- 
tance from the photosphere increases. These observa- 
tions have been very closely examined by Prof. Tacchini 
and Mr. Lockyer, with the result that both these solar 
observers are now prepared to ascribe these new pheno- 
mena to the descent of relatively cool material. 
“It is difficult to over-estimate the importance of this 
result from the point of view of solar theory. The deter- 
mination of the direction of the currents in the solar 
atmosphere is indeed so important that it was included in | 
the programme of the observations to be made by Mr. 
Turner with his 4-inch finder, but no certain results were 
secured by this means, as the structure of the corona was 
apparently unusually complicated. In the spectroscope, 
however, one long streamer was observed to be much 
brighter near the limb, This is not absolutely conclusive 
evidence, but it has its value. 
‘““To return, however, to Prof. Tacchini’s other ob- 
servations. He found that the prominences which were 
visible both during totality and by the ordinary method 
presented very different appearances, so that we are 
driven to the conclusion that by the latter we only see 
part of the phenomena. This entirely accords with Mr. 
Lockyer’s recently published views, in which it is sug- 
gested that the metallic prominences seen near spots 
are really mixed up and down rushes, with probably an 
excess of the cooler descending material. Thus, for in- 
stance, the metallic prominences observed by the ordinary 
method after the eclipse were found to be only the 
central portions of those observed during totality, the 
part visible only during totality forming a whitish fiage 
round the more incandescent centre. Another very 
important observation was made. The ‘flash’ of bright 
lines, attributed by Prof. Young to the existence of a 
thin stratum which was supposed to contain all the 
vapours the absorption of which is registered by the 
Fraunhofer lines, was found to be due solely to the great 
reduction in the intensity of the light reflected by the 
earth’s atmosphere allowing the spectrum of the higher 
regions to be seen the moment the lowest stratum of the 
corona was covered by the moon. This is carrying the 
unveiling of the spectral effects by the increasing dark- 
ness recorded in the Egyptian eclipse to its furthest 
limit, and it harmonises all the observations of this kind 
made since the eclipse of 1870. 
“So much in the way of new facts and new ideas. We 
next come to the second kind of work, the testing of old 
ones. In this connection we have to refer to Mr. Turner’s 
work at Boulogne and Mr. Perry’s at Carriacou. Mr. 
Lockyer, before the eclipse of 1882, had been driven by a 
long series of experiments and observations to conclude 
that the lower part of the atmosphere was composed of 
successive strata giving different spectra, and that the 
sole cause of the difference was temperature. A test was 
possible during an eclipse, for then these lines of any 
substance seen to brighten when a higher temperature is 
employed in the laboratory should be seen shortest and 
He found that the prominences | 
| this year were the same as those recorded in 1882. 
brightest. The test was perfectly sharp and definite. It 
was applied during the eclipse of 1882, and the lines 
appeared as predicted. 
“So far, then, the hypothesis which had enabled a pre- 
diction to be made which was subsequently verified was 
worthy of confidence. But this was a reason for repeating 
the observations to put the hypothesis on a wider basis. 
Mr. Turner did this, and found that the facts observed 
It 
remains now for those who oppose Mr. Lockyer’s views to 
give a more simple and sufficient explanation of those 
facts than he has done. Mr. Perry was to have extended 
the test further, but he failed to make the critical obser- 
vation, as a large number of lines were seen, and those 
only for a short time, for the clouds came up directly after 
totality. 
“Capt. Darwin was charged with a test of a different 
order. It was stated, after the eclipse of 1871, that the 
light of the corona was in all probability strongly photo- 
graphic ; and in 1875 the evidence in this direction was 
greatly strengthened, and some attempts were made to 
utilise this quality to obtain photographs of the corona 
without an eclipse. The efforts failed. More recently 
Mr. Huggins has tried the same methods with great pre- 
cautions, and he has obtained appearances on his plates 
which resembled the corona, so that some thought that 
success had been achieved. The natural thing to do was 
to test the method during the progress of the eclipse to 
see if the appearances in question, due to atmospheric 
glare according to some, to the corona according to 
others, really resembled the corona when revealed by 
totality. Capt. Darwin’s work seems to leave no doubt 
that the effect is due to glare only, and that the corona 
has nothing to do with it. 
“Next as to new methods of attack. This year the only 
new method applied has been a change of the photo- 
graphic manipulator, with a view of obtaining a much 
larger number of photographs and increasing the size of 
the images at the same time, by using larger lenses of 
longer focus and secondary magnifiers. Along this line 
success has not been complete, because the photographs 
have not been actually taken, as this new work was under- 
taken by Mr. Lockyer and his party at Green Island, and 
was clouded out. In spite, however, of this want of photo- 
graphs, Mr. Lockyer will nct hear of want of success. He 
holds that the problem has been solved. 
“T have given an account of the work at Green Island, 
including the results of the rehearsals, and your readers 
will have been able in a large measure to form an opinion 
of their own. The improvement consists essentially in 
using four plates in one slide. The difficulty always has 
been in getting the slide in and out of position, so that 
the more plates we can work in one slide the more the 
difficulty and consequent loss of time are evaded. Another 
advantage lies in the use of a secondary magnifier, as by 
this means not only is the photographic image of the sun 
enlarged, but a system of cross wires can be introduced 
which permits of a perfect orientation of the picture ob- 
tained—that is, the exact east and west points on the cir- 
cumference can be determined with the utmost precision, 
_ and from this the position of the various phenomena with 
regard to the sun’s equator and poles. It can be easily 
imagined that on this point there must be no uncertain 
sound. 
“We next come to the photographic record obtained by 
old methods—that is, methods dating in the case of photo- 
graphy of the corona from 1852, and in the case of spec- 
trum photography from 1875. About twenty photographs 
of the corona have been obtained in all, and five photo- 
graphs of the chromosphere and lower regions of the 
corona. Mr. Maunder obtained seven of the corona, and 
could have obtained more, at Carriacou. Captain Darwin 
obtained six, and Dr. Schuster, we believe, five, at Prickly 
Point. 
ee 4 Eneerm © ee 
Of the photographs seven spectra, two with the - 
—— 
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