The Romance of the Heavens 19 



observer, the late Professor Tacchini of Rome, observed one 

 of the greatest prominences ever seen by man. Its height 

 was no less than 142,000 miles eighteen times the diameter 

 of the earth. Another mighty flame was so vast that sup- 

 posing the eight large planets of the solar system ranged 

 one on top of the other, the prominence would still tower 

 above them. 1 



The fourth and uppermost layer or region is that of the 

 corona, of immense extent and fading away into the surrounding 

 sky this we have already referred to. The diagram (Fig. 5) 

 shows the dispositions of these various layers of the sun. It is 

 through these several transparent layers that we see the white 

 light body of the sun. 



2 



The Surface of the Sun 



Here let us return to and see what more we know about the 

 photosphere the sun's surface. It is from the photosphere that 

 we have gained most of our knowledge of the composition of the 

 sun, which is believed not to be a solid body. Examination of the 

 photosphere shows that the outer surface is never at rest. Small 

 bright cloudlets come and go in rapid succession, giving the 

 surface, through contrasts in luminosity, a granular appearance. 

 Of course, to be visible at all at 92,830,000 miles the cloudlets 

 cannot be small. They imply enormous activity in the photo- 

 sphere. If we might speak picturesquely the sun's surface re- 

 sembles a boiling ocean of white-hot metal vapours. We have 

 to-day a wonderful instrument, which will be described later, 

 which dilutes, as it were, the general glare of the sun, and enables 

 us to observe these fiery eruptions at any hour. The "oceans" of 

 red-hot gas and white-hot metal vapour at the sun's surface are 

 constantly driven by great storms. Some unimaginable energy 

 streams out from the body or muscles of the sun and blows its 

 outer layers into gigantic shreds, as it were. 



1 The Romance of Astronomy, by H. Macpherson. 



