ave been to some
extent--though we may be sure not completely--penetrated.

On June 30, 1861, the earth passed, for the second time in the century,
through the tail of a great comet. Some of our readers may remember the
unexpected disclosure, on the withdrawal of the sun below the horizon on
that evening, of an object so remarkable as to challenge universal
attention. A golden-yellow planetary disc, wrapt in dense nebulosity,
shone out while the June twilight of these latitudes was still in its
first strength. The number and complexity of the envelopes surrounding
the head produced, according to the late Mr. Webb,[1192] a magnificent
effect. Portions of six distinct emanations were traceable. "It was as
though a number of light, hazy clouds were floating round a miniature
full moon." As the sky darkened the tail emerged to view.[1193] Although
in brightness and sharpness of definition it could not compete with the
display of 1858, its dimensions proved to be extraordinary. It reached
upwards beyond the zenith when the head had already set. By some
authorities its extreme length was stated at 118 deg., and it showed no
trace of curvature. Most remarkable, however, was the appearance of two
widely divergent rays, each pointing towards the head, though cut off
from it by sky-illumination, of which one was seen by Mr. Webb, and both
by Mr. Williams at Liverpool, a quarter of an hour before midnight.
There seems no doubt that Webb's interpretation was the true one, and
that these beams were, in fact, "the perspective representation of a
conical or cylindrical tail, hanging closely above our heads, and
probably just being lifted up out of our atmosphere."[1194] The cometary
train was then rapidly receding from the earth, so that the sides of the
"outspread fan" of light shown by it when we were right in the line of
its axis must have appeared (as they did) to close up in departure. The
swiftness with which the visually opened fan shut proved its vicinity;
and, indeed, Mr. Hind's calculations showed that we were not so much
near as actually within its folds at that very time.

Already M. Liais, from his observations at Rio de Janeiro, June 11 to
14, and Mr. Tebbutt, by whom the comet was discovered in New South Wales
on May 13, had anticipated such an encounter, while the former
subsequently proved that it must have occurred in such a way as to cause
an immersion of the earth in cometary matter to a depth of 300,000
miles.[11