also been made with the
interesting result of showing that during an eclipse the Moon's power to
reflect solar heat to the Earth sensibly declines.

The duration of an eclipse of the Moon is dependent on its magnitude.
Where the eclipse is total the darkness, or what counts for such, may
last for nearly 4 hours, though this is an extreme limit rarely
attained. An eclipse of from 6 to 12 digits (to use the old-fashioned
nomenclature which has been already explained) will continue from 21/2 to
31/2 hours. An eclipse of 3 to 6 digits will last 2 or 3 hours, and a
smaller eclipse only 1 or 2 hours. The visual observations to be made in
connection with partial or total eclipses of the Moon chiefly relate to
the appearances presented by our satellite when immersed in the Earth's
shadow. On such occasions, as has been already stated, it frequently
happens that the Moon does not wholly disappear, but may be detected
either with a telescope or even without one. It may exhibit either a
dull grey appearance, or more commonly a pinkish-red hue to which the
designation "coppery" is generally applied. Perhaps the most remarkable
instance of this was the eclipse of March 19, 1848.

Mr. Forster who observed the phenomenon at Bruges thus describes[117]
what he saw:--"I wish to call your attention to the fact which I have
clearly ascertained, that during the whole of the late eclipse of March
19 the shaded surface presented a luminosity quite unusual, probably
about three times the intensity of the mean illumination of the eclipsed
lunar disc. The light was of a deep red colour. During the totality of
the eclipse the light and dark places on the face of the Moon could be
almost as well made out as on an ordinary dull moonlight night, and the
deep red colour where the sky was clearer was very remarkable from the
contrasted whiteness of the stars. My observations were made with
different telescopes, but all presented the same appearance, and the
remarkable luminosity struck everyone. The British Consul at Ghent, _who
did not know there was an eclipse_, wrote to me for an explanation of
the blood-red colour[118] of the Moon at 9 o'clock."

In striking contrast to this stands the total eclipse of Oct. 4, 1884,
which is described by Mr. E. J. Stone[119] as "much the darkest that I
have ever seen, and just before the instant of totality it appeared as
if the Moon's surface would be invisible to the naked eye during
totality; but such was no