STRANGE NEWS ABOUT THE SOLAR PROMINENCES. 
49 
plumes are not also jets. The real distinction appears to be 
that in jets a part of the photosphere is lifted up, while 
in the case of plumes it is only the chromatosphere which is 
disturbed. It does not appear to be established as a fact that 
all prominences require an orifice of projection, and still less 
that the height of protuberances can be taken as a measure of 
the pressure which has projected the gaseous stream, since 
plumes have been seen to form themselves in the masses sus- 
pended in the free atmosphere, far above the possibility of a 
liquid origin. The persistence of plumes is very remarkable 
as compared with the continuance of the sheaves. In spite of 
the great mobility of the former, they may be found for two or 
three days in the same place ; towards the poles their existence 
lasts still longer. On the other hand, the most beautiful 
sheaves generally last but a few minutes, in very rare cases 
a few hours. This confirms me in the opinion that sheaves 
are due to a veritable eruption, taking place at a great depth, 
the matter composing them having an exceedingly high tem- 
perature, and being propelled with immense velocity. The 
presence of jets and sheaves is the most certain sign that a 
spot is imminent. As to the connection between protuberances 
and the faculce , it may be stated that jets, whatever may be 
their shape, are invariably accompanied by faculge ; but that 
plumes, more particularly if they are small, are often seen 
where there are no faculge. A peculiarity worthy of notice is 
the feebleness of the light from prominences near the pole — an 
indication, as I have before stated, of less activity and a less 
powerful propelling force. The protuberances, both as to num- 
ber and size, are in accordance with the solar activity as mani- 
fested by the spots ; the fewer the spots the less numerous and the 
less extensive are the protuberances likewise. The dimensions 
of the protuberances are very variable. The largest that I 
have seen for some time have not exceeded four to four and a half 
minutes, from which it may be concluded that from the origin 
of their mass, their measure would be at least five to six 
minutes, being the height assigned by eclipse-observers to the 
highest part of the corona. The jets are in general not so 
high, seldom exceeding one to three minutes.” 
It will be evident that Secchi’s observations bear in a most 
important manner on the question of an association between 
the prominences and the solar spots, though they do not make 
quite clear the nature of the connection. Further evidence is 
wanted before we can be sure that the eruption-prominences are 
directly connected with the outbreak of spots on the photo- 
sphere. Now Professor Young’s researches have supplied (as it 
appears to me) just the evidence which was required. He has 
actually witnessed the eruption of matter from the sun, and he 
VOL. XI. — NO. XLXI. E 
