134 
POPULAE SCIENCE EEVIEW. 
exchanging accurate time-signals by electric telegraph : Green- 
wich was to give its time to Gibraltar, and Gibraltar to return 
its time to Greenwich ; Gibraltar local time being accurately 
determined at Professor Newcomb’s temporary observatory. 
This exchange was to be made on several days before and after 
the eclipse through the medium of the Falmouth and Gibraltar 
cable, but, as may be remembered, the cable broke early in 
December, and it was not repaired till long after Professor 
Newcomb had left the Eock. His observations are consequently 
useless until another opportunity offers for effecting the longi- 
tude determination : then they can be made available. 
The eclipse has therefore been of some import to metrical 
astronomy. Let us now take a glance at the materials which 
have been gleaned from it towards a solution of the physical 
questions at issue at the time of its occurrence, and to which 
it was appealed to decide. Of the phenomena revealed when 
the moon hides the photosphere of the sun, the corona only 
remains enigmatical. Baily’s heads were long ago explained 
out of interest, and the red prominences now no longer need 
an eclipse to bring them under study. The object the most 
striking and the most anciently remarked * is still the most 
bewildering. At the time of the eclipse four modes of obser- 
vation were at hand to resolve the mystery of its nature. First, 
eye-sketches, with or without telescopic aid, to decide whether 
the corona is similarly depicted by observers near together and 
far apart. Second, photographic pictures, which would give 
the aspect of the corona free from personality (though they 
may include subjective appearances of photo-chemical cha- 
racter). Third, spectroscopy, to determine the gaseous or 
incandescent solid condition of the original source of the 
coronal light. Fourth, polariscopy, which it was hoped would 
show whether that source is in the corona itself or apart from 
* Dr. Schmidt, of Athens, calls attention to the following account of an 
eclipse seen at Corfu in a.d. 968, in which the corona is very clearly de- 
scribed : — u Leon, the deacon, reports thus concerning the eclipse. 1 The 
appearance of the eclipse was of this nature : December was carrying on its 
22nd day, and in the fourth hour of the day, the sky being clear, darkness 
covered the earth, and the brightest stars appeared ; and it was possible to see 
the disc of the sun obscure and without brightness, but with a certain radiance, 
faint and pale, in the manner of a fine band shining in a circle round the 
disc along its outer edge : and the sun, overlapping the moon a little (for 
she appeared directly intercepting him), sent out its own rays and filled the 
earth with light.’” The date curiously coincides with that of the last 
eclipse, though it is Old] Style reckoning. The appearance of the stars 
seems to prove that the eclipse was total : it is marked so in the reliable 
list of Eclipses given in the Art de Verifier les Dates des Faits Historiques. 
