SCIENTIFIC SUMMARY. 
383 
state of change. Having examined minutely very small portions of the 
sun’s surface with very high powers of his solar eyepiece, he has been able 
to keep the same luminous masses and their intervening pores in sight for 
an hour or two together, and has rarely seen any decided change in either, 
though he has noticed that very slight atmospheric tremours will give such 
an appearance. In the immediate neighbourhood of spots which are 
rapidly enlarging or closing, this tranquillity, however, is no longer 
observed, and the luminous masses become more elongated. This change 
is the more remarkable in those cases where the spot is divided by a bridge 
which passes out from the penumbra, when the luminous masses take the 
appearance of bits of straw, and seem to be “ preparing for a rush across 
the chasm.” These bridges, he finds, are always formed by the bright 
streaks of the outer stratum. Mr. Dawes calls attention to the very dark 
spot frequently seen in the umbra, the former being the true nucleus, whilst 
the latter is improperly termed so. He finds that the pores are not quite 
round, but appear like fissures — not black, but of a dark grey. He has no 
doubt but that the bright faculee are ridges, as he has seen them actually 
project beyond the limb of the sun, like the mountains at the edge of the 
moon. He is, however, of opinion that the less luminous masses do not 
mingle with the brighter ones, although they are on the whole at the same 
level. The umbra he considers to be a cloudy and imperfectly transparent 
cloudy stratum, the penumbra as self-luminous, making the second 
envelope, and the third envelope is the photosphere. The very deep spots, 
he thinks, are formed by an immense volume of non-inflammable gas 
from the surface of the sun, which latter he imagines to be the nucleus or 
darkest points of the umbra. The superficial spots are considered by him 
as convulsions in the photosphere itself. 
With the large Greenwich refractor, Mr. Stone observes the sun’s photo- 
sphere to have an appearance similar to that as if it were covered with 
grains of rice. It has been remarked that it is probable that the willow 
leaves of Mr. Nasmyth, the particles of straw of Mr. Dawes, and the above 
description of Mr. Stone, are one and the same phenomenon. 
Comet of December 28, 1863. — This comet came very near the earth in 
the month of January ; but it was not visible to the naked eye, although 
expected to be so. It is interesting, however, to know that it appears to 
be one of the periodical class ; and it has been concluded to be identical 
with those of 1490 and 1810. If its suspected period of fifty-three years 
be correct, it should of course have appeared about the years 1543, 1596, 
1649, 1703, and 1757 ; but its faintness on the present occasion, when it 
required a good telescope to perceive it, may account for its invisibility at 
those times. In 1490 it is described as having a very long and white tail, 
which was turned towards the east, and followed the sun after setting. It 
is described as having been visible from the feast of the Epiphany to the 
middle of February. The comet of 1810 was discovered on August 22 of 
that year by M. Pons, and was seen by him to October 8 of that year. 
It does not appear to have been visible to the naked eye on that occasion, 
and it is described as being round, with a faint nebulosity. The observa- 
tions, both in 1490 and 1810, were rough and uncertain ; but the identity 
of the two comets, as deduced from their similar paths and motions in space, 
