NATOK E 
599 
THURSDAY, APRIL 14, 1870 
LHE TOTAL SOLAR ECLIPSE OF DECEMBER 
NEXT 
ON Friday last, Mr. Lassell, the president, brought before 
the Royal Astronomical Society the subject of the 
total solar eclipse of December next, with a view to elicit- 
ing information as to the steps necessary for observing it. 
A most interesting discussion ensued, in which the 
Astronomer Royal, the president, Messrs. Dela Rue, Stone, 
and Huggins, Admiral Ommaney, Colonel Strange, and 
Lieutenant Browne, R.A., took part. The line of totality 
passes near the following places :—Odemira, in Portugal, 
Cadiz, Estepona (about twenty miles north of Gibraltar), 
Oran, on the Algerine coast, Syracuse, and the region 
including Mount Etna in Sicily. 
The duration of totality will be a little over two minutes 
of time. It is proposed that an endeavour shall be made 
to equip two expeditions to observe the phenomena of the 
eclipse at two of these points, in order that, should 
adverse weather occur at one station, results may be, 
perhaps, obtained atthe other. Itis thought probable that 
the station of Oran, in Algeria, will be occupied by a French 
party of astronomers. The choice for English observers 
seems to be between Cadiz, Gibraltar, and Syracuse. 
Both Admiral Ommaney and Lieut. Browne, R.A., spoke 
from personal experience favourably of the climate of 
Gibraltar at that time of the year. The speakers were 
unanimous in considering that both parties ought to be 
equipped for the following main objects:—(1) Photography; 
(2) Spectrometry; (3) Polarisation. Other objects of 
subsidiary importance, as Photometry and Meteorology, 
would also receive due attention. An approximate esti- 
mate of personal and instrumental force gives from 20 to 
25 skilled observers, and about ro telescopes of from 4 to 
6 inches aperture, as the complement necessary for each of 
the two expeditions. 
The first step which the Council propose to take is to 
invite, by circular and other means, those prepared to 
volunteer for this service to send in their names at once, 
specifying the particular class of observation which the 
observer desires to be engaged in. The number of ac- 
tually available telescopes and instruments will also be 
ascertained. 
When this preliminary information has been acquired, 
the Council of the Royal Astronomical Society, which has 
resolved itself into a committee for the purpose, will then 
consider whether they should apply to Government for 
such assistance as may enable them to utilise, with the 
utmost advantage, their own resources. Pending the 
collection of this information, it would be premature to 
attempt any estimate of the public assistance which may 
be required to guarantee the success of this enterprise. 
But it is not too early to lay before our readers some idea 
of its character and importance. 
The systematic examination of the solar surface is 
emphatically a modern study, which has, even during the 
last twelve months, advanced with enormous strides. 
Until recently these researches were limited to the ocular 
inspection and photographic representation of features 
rendered visible at ordinary times by our improved 
telescopic power, and to similar modes of examining 
certain other features developed during eclipses. Sub- 
sequently, with the wonderful aid afforded by the spectro- 
scope, a new class of phenomena was brought under 
examination, but only momentarily, on the rare occasions 
of total solar eclipses. Only last year M. Janssen and 
Mr. Lockyer, labouring independently, showed that many 
of the spectroscopic observations, for securing which an 
eclipse had been believed to be indispensable, could be 
made without the aid of that phenomenon,—a discovery 
second, in dignity and value, to none that this age has 
achieved. But these very methods have opened out 
inquiries and doubts which again require for their 
solution the peculiar circumstances attending total 
obscuration of the sun’s disc. 
For instance, the corona which has been seen at times 
to extend to a distance beyond the sun greater even than 
the sun’s diameter, has been very generally stated to in- 
dicate a solar atmosphere, a conclusion not entirely borne 
out, however, by the spectroscopic method of investiga- 
tion; and Dr. Frankland and Mr. Lockyer have stated 
their opinion that the who/e of the corona can hardly be 
solar—this opinion being based partly on their approxi- 
mate determination of the pressure in these regions. This 
question was manfully attacked during the eclipse ob- 
served last year in America, but the results, which will be 
found most carefully detailed in the report printed by 
the American Government, were not conclusive. 
Again, it has been shown that the solar chromosphere 
is not entirely seen by the new method of observation ; 
away from the sun its light is ordinarily so feeble that it 
cannot be detected through our brighter atmosphere, but 
during eclipses it is seen; and in this matter the American 
astronomers did admirable work, which, however, requires 
strengthening, for many still hold that the radiance depicted 
on the photographic plates immediately round the moon 
in the photographs, is not the chromosphere, as stated by 
Dr. Gould and others, although there are very many argu- 
ments which can be brought forward in favour of their 
idea that it is that envelope. Other points might easily 
be brought forward to show the extreme and, in fact, 
special importance of eclipse observations at the present 
time. 
If researches such as these yielded no fruits beyond the 
satisfaction of our craving desire to know more of the 
structure and constitution of the sun, they would still be 
prosecuted with ardour. But the knowledge they are 
calculated to advance has a much wider range and a 
more tangible character than the gratification of philo- 
sophical curiosity. Sabine, Lamont, and Wolf many 
years ago detected the contemporaneity of magnetic 
disturbances and the maximum outbreak of spots on the 
sun’s surface. More recently De la Rue, Stewart, and 
Loewy have established a relation between the sun spot 
maxima and the configuration of the planets Venus and 
Jupiter. Systematic observations have been carried 
on at the Kew Observatory continuously for nine years 
for the express purpose of throwing light on the apparent 
connection of the sun spots with magnetic and planetary 
phenomena. During this period upwards of nine thou- 
sand photographic pictures of the solar disc have been 
taken. These researches, and those of Carrington, ex- 
tending over many years, have shown that though the 
spots, if observed from day to day and month to month, 
