THE SUN.

35

group of faculm upon the photosphere. If it continue, a fierceeruption, or series of eruptions and explosions, next occurs, infiery fury passing all our powers of imagination, and presently,as above described, a spot, or group of spots, appears.

The drawings in Plate III. may serve to illustrate the pre-ceding remarks. The first is a general view of the Sun, takenfrom a sketch made by Tacchini at Palermo in April 1870,and published in vol. vi. of the Memoirs of the Italian Spectro-scopical Society previously referred to. It shows the occurrenceof faculee in other parts of the solar surface as well as in thetwo parallel zones on opposite sides of the equator, in which alarge number of spots of various sizes are seen.

The other two drawings are elaborated and enlarged fromthose made by Professor Ricco, at Palermo, of two spotsobserved on May 27th and May 28th, 1880, and published invol. ix. of the above Memoirs.

They clearly show the dark umbra, or central portion of thespot, as well as the surrounding penumbra, or less darkportion. An attempt has also been made to indicate theway in which the filaments of the photosphere are apparentlydrawn inwards towards the umbra, so that by their convergencethe lower part of the penumbra is brighter than its upperportion.

Indications may also be seen, in the left-hand and right-handdrawings respectively, of the way in which isolated portions ofthe photosphere occasionally float across, or form a bridge over,the depression, or (to use Professor Young’s graphic term)the sink, of which a spot consists.

Both within the cavity of a Sun-spot and in the prominences,the spectroscope enables us, by certain distortions and slightchanges in the position of the bright lines which it shows, todetermine the velocity and direction of the motion of some ofthe huge masses of vapour involved. It is in this way, as wellas by the general appearance of a spot, that we are assured oftheir occasional rotatory movements ; or, to use more popularlanguage, that we see in them veritable cyclones of fire.

We are aware that a theory has recently been suggested thatsome of all this vast turmoil and almost inconceivably rapid