50 
POPULAK SCIENCE KEVIEW. 
has afforded ns the means of measuring the energy of ejection 
and the velocity with which the ejected matter rushes through 
the lower strata of the solar atmosphere. 
On September 7, at noon, he had been examining with the 
telespectroscope an enormous hydrogen cloud on the eastern 
limb of the sun. 44 It had remained,” he says, 44 with very 
little change since the preceding noon,” a long, low, quiet-look- 
ing cloud, not very dense or brilliant, nor in any way remark- 
able except for its size. It was made up mostly of filaments 
nearly horizontal, and floated above the chromatosphere with 
its lower surface at a height of some 15,000 miles, but was 
connected with it, as is usually the case, by three or four 
vertical columns brighter and more active than the rest. In 
length it measured 3' 45", and in elevation about 2" to its upper 
surface ” (that is, it was 100,000 miles long by 54,000 miles 
Fig. 1. 
high). At half past twelve Professor Young was called away 
for a few minutes. At that time, 44 there was no indication of 
what was about to happen, except that one of the connecting 
stems at the southern extremity of the cloud had grown con- 
siderably brighter, and was curiously bent to one side ; and near 
the base of another at the northern end a little brilliant lump 
had developed itself, shaped much like a summer thunder- 
head.” 
On returning, though less than half an hour had passed, 
Professor Young found to his great surprise that 44 in the 
mean time the whole thing had literally been blown to shreds 
by some inconceivable uprush from beneath.” 44 In place of 
the quiet cloud I had left,” he says, 44 the air, if I may use the 
expression, was 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 
