THE SUN. 85 



of square miles, are by no means uncommon. One spot 

 which I measured in the year 1837 occupied no less than 

 three thousand seven hundred and eighty millions, taking 

 in all the irregularities of its form ; and the black space 

 or "umbra " in the middle of one, which was very nearly 

 round, would have allowed the earth to drop through 

 it, leaving a thousand miles clear of contact on every 

 side: and many instances of much larger spots than 

 these are on record. What are we to think, then, of the 

 awful scale of hurricane and turmoil and fiery tempest 

 which can in a few days totally change the form of such 

 a region, break it up into distinct parts open up great 

 abysses in one part, such as that I have just described, 

 and fill up others beside them ? As to the forms of the 

 spots, they are so conspicuously irregular as to defy de- 

 scription. 



(42.) But we must proceed, for there are more won- 

 ders yet to relate. Far beyond the photosphere, or 

 brilliant surface of the sun, extends what perhaps may 

 be considered as its true atmosphere. This can only 

 be seen at all in the rare opportunities afforded by total 

 eclipses of the sun. Everybody knows that an eclipse of 

 the sun is caused by the moon coming between it and 

 us. Now, by an odd coincidence, it so happens that 

 the sun being 400 times farther off than the moon, is 

 also ALMOST exactly, but a trifle less than 400 times as 

 large in diameter; so that when the centre of the moon 

 comes exactly in the line with the centre of the sun it 

 appears to cover it, and a very little more, so as to pro- 

 ject on all sides a very little beyond it. Now, as the 



