STRANGE NEWS ABOUT THE SOLAR PROMINENCES. 
53 
suitable observing weather, at American and European stations. 
Professor Young in America, and in Europe Lockyer, Janssen, 
Secchi, Respighi, and Zollner, with the few others who take a 
more or less systematic part in the work, are unable to devote 
the whole of the day — or probably even a large portion of the 
day — to observation of the sun. But apart from this we must take 
into account the occurrence of unfavourable observing weather, 
and Lockyer speaks of days seemingly fine, when certain indi- 
cations in the appearance of the prominence-lines assure him 
that observation is useless. Doubtless the experience of other 
observers resembles his in this respect. But this is not all. 
During a great part of the 24 hours the sun is not above 
the horizon at any of the European or American observing 
stations. And then, lastly, even when he is above the horizon, 
solar outbursts of enormous importance might take place with- 
out any possibility that terrestrial observers could become 
cognisant of the fact; simply because any outbursts in the 
central parts of the face turned towards the earth and of the 
half turned directly away from the earth, could not produce 
prominence-phenomena outside the solar limb. The spectroscope 
gives us an account indeed of disturbances taking place on the 
sun’s face ; but the account can be by no means so easily in- 
terpreted as in the case of prominences seen in the ordinary 
manner. 
When we combine these considerations with the circumstance 
that a solar eruption lasts but a few minutes, and that the 
observer is unable to examine more than one portion of the 
sun’s limb at a time, so that many important eruptions might 
occur even while he was engaged in the most attentive observa- 
tion, we see that outbursts like the one witnessed by Professor 
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 im- 
portant 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 carefully 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 
