200 LIGHT SCIENCE FOR LEISURE HOURS. 



northern end a little brilliant lump had developed 

 itself, shaped much like a summer thunderhead.' 



On returning, though less than half an hour had 

 passed, Professor Young found to his great surprise 

 that ' in the mean time the whole thing had literally 

 been blown to shreds by some inconceivable uprush 

 from beneath.' ' In place of the quiet cloud I had 

 left,' he says, ' the air, if I may use the expression, was 



Fio. 1. 



filled with flying debris a mass of detached vertical 

 fusiform fragments, each from 10" to 30" long by 2" 

 or 3" wide, brighter and closer together where the 

 pillars had formerly stood, and rapidly ascending. 

 When I first looked some of them had already reached 

 a height of nearly 4' (100,000 miles); and while I 

 watched them they rose, with a motion almost per- 

 ceptible to the eye, until in ten minutes (1 h. 5 m. 

 P.M.) the uppermost were more than 200,000 miles 

 above the solar surface. This was ascertained by 

 careful measurements ; the mean of three closely ac- 



