224 Original Articles. | April, 
indeed excessively so. As there occur umbre without penumbre, so 
penumbre occur without umbre, but such are usually only branches or 
outlying portions of groups, or the remains of a spot in the act of 
obliteration when the umbra has disappeared. In the great majority 
of cases many umbre are surrounded and connected into a group by a 
common penumbra. This indeed is almost always the case with large 
spots. The umbre, when large, affect more compact and rounded forms 
than the penumbre, and the interior nuclet of Mr. Dawes still more so. 
On the whole there is a certain tendency to the bizarre in all the forms, 
which though indescribable in words is highly characteristic. One of 
Mr. Howlitt’s drawings offers a strange approximation to the complete 
form of a human skeleton. A form not uncommon, especially towards 
the subsidence of a period of solar activity, is that of a tadpole with a 
large irregular head consisting of a penumbra and several umbre, and 
a curved penumbral tail dotted with smaller ones (see Figs. 4, 8). This 
form of spot has been noticed by some observers, among others by 
Picard in 1671, as recalling the outline of a scorpion (Fig. 6). The 
larger umbre are often crossed (Fig. 1), or nearly crossed (Fig. 2), by 
narrow bridges of light, rarely penumbral, most usually of the full 
brilliancy of the photosphere, or even surpassing it. In many cases 
they are irregularly rounded on three sides, and sharply cut as if 
snipped by scissors on the fourth, and to such sharp edges there is 
often no penumbral border. ‘Lastly, spots are much more commonly 
connected in groups than quite insulated,and very frequently affect linear 
sequences, oblique to the parallel of solar latitude in which they occur ; 
the line of direction being towards a point in the sun’s equator preceding 
the situation of the spot in longitude (see Fig. 7). 
Large spots, or groups, are almost always attended by neighbouring 
facule, which are streaks, or vein-like appearances, more or less crooked 
and branching, of brighter light than the general photosphere. They 
are much more conspicuous, however, near the borders of the visible 
disc than towards its centre, a fact strongly indicative of their eleva- 
tion, as ridges or heaps of the luminous matter, which so rising above 
the denser regions of the circumfused atmosphere, have their light 
proportionally less enfeebled by its absorption. On the other hand they 
are never traced fairly up to the actual edge of the dise—where the 
absorption of the solar atmosphere is so great as to extinguish (according 
to Chacornac) nearly half the light—a proof that their elevation is far 
from commensurate with the extent of that atmosphere, and that they are 
not identical with the “red flames” seen on the limb of the sun in total 
eclipses. Indeed the latter appear indiscriminately round every portion 
of the dise, whereas the facule are never seen in the sun’s polar regions. 
Neither is the connection of the spots with facule one of reciprocity, 
for the latter are often seen where no spots exist. 
When spots on the sun’s surface are viewed from day to day, they 
are seen to undergo great changes in form, size, and relative situation 
inter se, as well as to be carried round by a common movement ; 
evidently due to the sun’s rotation on its axis in the same direction, 
and nearly in the same plane as that of the planetary movements ; and 
