14 
plays of Aurora Borealis, which culminated in the great magnetic 
storm of Novemher 17th, the most intense recorded, and its 
accompanying magnificent aurora. The area of the spot on this 
day was a maximum, being 2,417, or nearly 2,7613 millions of 
square miles. The June spot of 1883 was first seen on the 2nd 
near the centre of the disc, its length being about one-tenth of 
the sun’s diameter, or 85,000 miles, and yet not the slightest 
vestige of it was discernible on May 30th. Another spot was 
followed during the successive rotations of the sun from October, 
1883, to January, 1884. 
Should the definition be very good, it is observed that the 
mottled surface of the solar disc is in a state of constant change 
and commotion. These changes are very minute and rapid, and 
require a most constant and patient watch to detect them. The 
magnificent photographs of M. Janssen, of Mendon, had shewn 
that in parts the mottled surface puts on an appearance of 
blurring, and Trouvelot, in 1876, called attention to minute 
evanescent spots which he termed ‘‘ veiled spots.” These veiled 
spots have been the subject of constant study at Stonyhurst 
during the last three years, and they have been classified and 
the manner of their appearance indicated. They are found in 
every portion of the disc, and are seldom absent for any con- 
siderable time. A few minutes suffice for their appearance and 
disappearance, and they are frequently accompanied by facule. 
In colour, they are of a cold grey tint, and are never well defined. 
Some are seen as a slight cloud, which rapidly changes its out- 
lines, becomes fainter, and disappears. A second class are 
observed first of the form of a round black dot, which becomes 
diffused into a cloud-like mass, and very soon vanishes. To a 
third class the name of “ sub-permanent”’ spots has been given, 
as they seem to be intermediate between spots of the ordinary 
permanent type and veiled spots. They last sometimes for 
several days, but are always ill-defined and unlike the ordinary 
dark pores of the solar surface. Their comparative permanence 
distinguishes them from the other classes of veiled spots, and 
their ill defined or misty appearance is the only difference between 
them and ordinary spots. Moreover, their shape is irregular, 
and their proportions never equal those assumed at times by 
other veiled spots. Perhaps they are the last traces of a spot as 
it sinks into the photosphere, and sometimes the first signs of 
those that never become perfectly developed. 
And now, before closing our view of solar phenomena, we 
may glance at the main outlines of a theory propounded by the 
Jate Padre Secchi, which explains the chief facts observed. 
According to this distinguished physicist, the solar spots are the 
effects of an uprush of matter from the interior of the sun. This 
matter, consisting of heavy metallic vapours, among which iron, 
