504 Bei'. S. J. Perry [May 24, 



the sun as it depicts itself upon the drawing-board, we soon perceive 

 that no i^art of the surface is long at rest. Everywhere are seen 

 small dark shadowy objects, attracting special attention now in one 

 place and then in another, sometimes forming groups, and at other 

 times almost compauionless, affecting no special zone, and combining 

 with no other form of solar marking, except occasionally with a few 

 bright faculse. 



These dim ill-defined objects seem first to have been observed in 

 1875 by Trouvelot, who gave them the name of veiled spots. They 

 soon forced themselves into notice w^hen our daily sun- work was 

 started at Stonyhurst, and ever since they have never failed to be 

 carefully watched. At first they were divided, for convenience, into 

 three classes, but on further examination there seems to be no need 

 of more than a single distinction. When they first catch the eye all 

 IH'esent much the same general appearance, resembling small frag- 

 ments of ill-defined penumbra, but their position on the disk, and 

 still more their duration, soon enable the observer to distinguish the 

 class to which they belong. Those of the first class appear in all 

 heliographic latitudes, and never remain visible for more than two or 

 three minutes ; whilst the others, which have been called sub-permanent 

 spots, are confined exclusively to the spot zones on either side of the 

 equator, and this class may remain on the disk for two or more days. 

 Sub-permanent spots are not always to be found on the surface of the 

 sun, their tint is a shade less dull than that of the other veiled spots, 

 and occasionally there is almost the appearance of an umbra in their 

 midst, though this rarely could be mistaken for a true umbra. For 

 even when their shading is in some parts more intense than in others, 

 the whole remains always ill-defined, and the limits of its several 

 parts are hard to distinguish. Frequently these dim objects show 

 themselves in considerable numbers in the neighbourhood of fully 

 developed spots, but then the latter are generally approaching their 

 time of dissolution. They may, perhaps, aptly be described as 

 imperfectly developed, or penumbral spots, and consequently be 

 included in the ordinary spotted area. But it is quite otherwise 

 with the first class of veiled spots, which except for their diminished 

 brilliancy would have nothing in comman with the fully developed 

 sun-spots. Seen in all solar latitudes, they are never absent from the 

 sun, being, with good definition, as frequent and as visible at the 

 epoch of spot maximum as at minimum, but catching the eye more 

 readily when markings more intense are absent from the surface. 

 The most striking characteristic of this class of spots is the rapidity 

 with which they invariably disappear ; but although no individual 

 spot ever lasts more than about three minutes, the first seen may be 

 joined in quick succession by a multitude of others similar to itself, 

 and thus transform vast areas, and give to portions of the solar surface 

 that blurred appearance which is so marked a feature in Janssen's 

 magnificent sun-pictures. The general distribution of these faint 

 objects, their evanescent character, and their ill-defined appearance, 



