KNOW l.i:i)(.l.. 



I-I IIKIAKV, ]')\. 



Till riiorosi'iii Ki:. Ri vi:i<siNc. Layi:i< and 



ClIKDMiiSI'IIKKi;. 



Tlif iiKiin luminosity of tlic Sun ori},'in;itLS in a 

 surfaro of inU-nso liriiliancy, called the photosplurc. 

 This is probably tlu- limit of acrf)static pressure ; :ill 

 above it bein^,' dynamically supjiortcd. I'irst, then' 

 is a rare kind of atmosphere of metallic vapours 

 some six hundred miles thick. It is called the 

 reversing layer, because in it a|)|Har to be the elements 



FiGl'Rl- 50. Iron Flocciili. 



that produce the chief dark lines of the solar spectrum. 

 .\bove this again is a still rarer la\-er of an atmos- 

 phere of hydrogen and other excessively light gases. 

 This is called the chromosphere, because of its 

 reddish colour. It appears to extend some thousands 

 of miles above the Sun's surface. 



In addition to the eight planets and their satt llites 

 and the belt of asteroids, a vast 

 luminous, apparently a meteoric, glow 

 surrounds the Sun in the plane of 

 the ecliptic. It is called the Zodiacal 

 light. It is probably so extensi\e as 

 to reach be\ond the orbit of tin 

 liarth : for when we look in a 

 direction away from the sun on a 

 clear dark night we see it in the form 

 of a glow called the Gegenschtin. 

 These myriads of particles would in 

 this |)osition be seen lit up by sun- 

 shine as the moon is when at its full. 



The Cokona. 



During a total eclipse, when fm ^i 

 few minutes the disc of the moon 

 completely hides the face of the sun 

 from view, not merely do we see the 

 great red flames of glowing hydrogen 

 and the vast volcanic ejections of 

 blazing metals, but surrounding the 

 black disc of the new moon are white shining rays of 

 radiant light, looking like a superb encircling halo of 



auroral niys. This is calltil the corona, a kind of 

 crown of glorw seeming to till of the ruling power 

 of the majestic monarch whose potenc\' controls the 

 giant globes that form the subjects of his might\ 

 kingdom. 



Such is the Sun. What are the forces, agencies, 



and |)otencies that control his speed of combustion ; 



that produce his storms and tempests ? What is 



the character of the mechanism that is the cause of 



his superl) grandeur ? What are the 



laws of nature laid under contribution 



to urge and regulate this seething 



mass of blazing gas ? How can 



convection act to bring heat from the 



interior of a mass a thousand times 



as rigid as the strongest steel ? 



What [Hishing force can be at 

 work urging the equatorial surface 

 of gas to slide over and move faster 

 than the general mass of the Sun ? 

 What originates the great solar 

 storms and what motive power keeps 

 for days and sometimes weeks, those 

 tremendous tornadoes, sweejjing the 

 surface of that vast glow ing furnace ? 

 What forces arc at work keeping up 

 tlu- reversing la\erand chromosphere? 

 Wliv do they not collapse and sink 

 '"■'"'"""''""''"'' (low 11 on to the Sun's static surface ? 

 What are the agents that create 

 ilu Milcanoes that emit the vast red 

 protuberances, and the still more wonderful metallic 

 flames. What causes these tongues of fire, that leap 

 upwards with velocities of hundreds of miles a 

 second, sometimes towering to a height of hundreds 

 of thousands of miles ? 



There are manv other questions that face the 

 solar student, and although scime of them may not 



///,./.>efvj//< /«* 



I'IGI'RK 51. HvdroL'cn Flocculi. 



in the present state of our knowledge be answered, 

 all at least are capable of receiving intelligible 



