x THE STARRY HEAVENS 383 
tional case, but a height of 100,000 miles is 
not unusual, and the velocity frequently 
reaches 100 miles in a second. 
The proverbial spots on the Sun in many 
respects resemble the appearances which would 
be presented if a comparatively dark central 
mass was here and there exposed by apertures 
through the more brilliant outer gases, but 
their true nature is still a matter of discus- 
sion. 
During total eclipses it is seen that the 
Sun is surrounded by a “corona,” or aureola of 
light, consisting of radiant filaments, beams, 
and sheets of light, which radiate in all direc- 
tions, and the true nature of which is still 
doubtful. 
Another stupendous problem connected 
with the Sun is the fact that, as geology 
teaches us, it has given off nearly the same 
quantity of light and heat for millions of 
years. How has this come to pass? Certainly 
not by any process of burning such as we are 
familiar with. Indeed, if the heat of the Sun 
were due to combustion it would be burnt up 
in 6000 years. It has been suggested that 
