A GREAT SOLAR OUTBURST. 211 



leaving out of consideration all the retardation ex- 

 perienced by the hydrogen before it reached the level 

 100,000 miles, its motion at that level corresponded to 

 an initial velocity much exceeding 255 miles per 

 second. But, if the retardation was so considerable 

 between the levels 100,000 miles and 200,000 miles, 

 as to reduce the hydrogen to rest at the last-named 

 level, whereas in vacua it would have reached a level 

 much exceeding 350,000 miles, how much more 

 effective must the retardation have been in the first 

 100,000 miles of the hydrogen's upward course? It is 

 difficult to express how much greater must be the 

 average density of the solar atmosphere between the 

 photosphere and a height of 100,000 miles, than 

 between the height 100,000 miles and 200,000 miles ; 

 but the disproportion must be enormous. Apart from 

 this, the retardation being always proportioned to the 

 velocity (though the law of this proportion is not 

 known), would have been much more effective in the 

 lower part of the hydrogen's course, on this account 

 alone. We have, then, this important conclusion (on 

 the hypothesis we are dealing with), that after travers- 

 ing a range of 100,000 miles from the sun's surface 

 under the action of a retardation enormously exceed- 

 ing that operating on the hydrogen in the observed 

 part of its flighty the uprushing hydrogen still retained 

 a velocity far exceeding that due to a velocity of 255 

 miles per second at the sun's surface in the case of a 

 projectile in vacuo- 



But we have now to consider towards which 

 p 2 



