A GREAT SOLAR OUTBURST. 205. 



Young may occur very frequently and yet be very 

 seldom seen. Again, the jet prominences seen by 

 Respighi, Secchi, Zollner, and others, though not 

 appearing to extend to the height reached by the 

 hydrogen wisps watched by Young, may (many of them)' 

 have reached to an even greater height, being reduced 

 by simple foreshortening; and as these are phenomena 

 frequently observed, we may not unsafely infer that 

 eruptions really as important as the one witnessed by 

 Professor Young are by no means uncommon. 



But let us consider what the facts observed by 

 Professor Young really imply. This is precisely one of 

 those cases where an observation requires to be care- 

 fully discussed in order that its full value may be 

 educed. 



Now the main point of the observation is this that 

 glowing hydrogen was observed to travel from a height 

 of less than 100,000 miles to a height of more than 

 200,000 miles in ten minutes. To be safe, let us take 

 the limiting heights at 100,000 miles and 200,000 

 miles ; and let us assume that there was no foreshort- 

 ening. These assumptions both tend, of course, to 

 reduce our estimate of the velocity with which matter 

 was ejected from the sun. 



Now we need not trouble ourselves by inquiring 

 whether the hydrogen wisps which moved upwards 

 before Professor Young's eyes were themselves ejected, 

 or whether their motion might not have been clue to 

 the ejection of other matter impinging upon these 

 wisps and forcing them upwards. Some matter must 



