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200,000 miles were then travelling upwards at the rate of 
about 150 miles per second. So acute an observer could not 
but have recognised the fact that the hydrogen was still in 
rapid upward motion at that time. We are compelled then, as 
I judge, to regard retardation as operative to at least some 
considerable degree in that upper half of the hydrogen’s 
course. 
This being so, I do not know that a single word of what I 
have said on the hypothesis of retardation being solely opera- 
tive need be altered. The italicised words at the close of the 
remarks made on that view must still be used in stating the 
conclusion to which careful reasoning would lead us. 
And here I approach the point to which these remarks have 
been tending. If we regard the hydrogen erupted or in motion 
in these jet prominences as not less dense than other matter 
partaking in the motion of primary ejection, the above conclu- 
sion, interesting as it is in itself, yet has no bearing on the 
subject of the corona. The erupted hydrogen reached a cer- 
tain enormous altitude, and there (so far as the extrusion of 
matter from the sun was concerned), the work of the solar 
eruption came to an end. But we have seen that the spectrum 
of the jet prominences indicates the presence of several other 
elements — amongst others, several metallic elements in the 
state of vapour. Now, it is highly probable that at a very 
early stage of the upward motion a large proportion of the 
metallic vapour would condense into the liquid form ; and if so, 
such liquid metallic matter would thenceforward meet with far 
less resistance, and so would travel to a far greater distance 
than the hydrogen. But without insisting on this point, we 
may yet feel assured that under similar conditions of tempera- 
ture and pressure the vapours of the metallic elements far 
exceed hydrogen in density. Thus they would from the 
very beginning of their upward course be exposed to a much 
less effective retarding influence. They would, therefore, 
retain a much greater proportion of the velocity primarily im- 
parted to the whole body of erupted matter ; nor is it by any 
means an unreasonable or unlikely supposition that at a height 
of 100,000 miles some of these constituents of the erupted 
matter would be travelling twice as rapidly upwards as the hy- 
drogen watched by Professor Young. So far, indeed, is this 
view from being unlikely that it is difficult to entertain any 
other opinion. Yet, on this view, the matter referred to would 
be travelling at a rate greatly exceeding 400 miles per second ; 
and a much smaller velocity would suffice to carry it away for 
ever from the sun’s controlling influence. Much more, there- 
fore, would the outrush of such matter suffice to explain the 
extension of the coronal streamers. 
