106 
NATURE 
| Fusnz 5, 1873 
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have hydrogen in a different condition altogether. We 
know that in this case we have a variation of velocity, 
because we get distinct changes in one direction or the 
other, 21a we get changes in both directions. We can 
determine by the amount of crookedness of the hydrogen, 
whether bright or dark, how far it is driven from its 
normal condition, and then how fast per second the 
hydrogen is travelling. In one case the velocity was 
something like 38 miles a second; in other words, we 
had heated hydrogen coming up at the rate of something 
Fic. 54.—Deviation of the F line in a spot-spectrum. 
like 38 miles a second, and cool hydrogen rushing down 
at something like an equivalent rate. Now, we are not 
only enabled, by a practical application of the prism, to 
determine these up and down rushes on the sun, by which 
we are enabled to learn much of its physical constitution, 
but also the rate at which storms travel over the sun— 
what we should call winds. The way that has been 
done will be perfectly clear on an inspection of the en~ 
graving (Fig. 55). It may appear strange to you that we 
should be able to observe a cyclone on the sun, but I 
hope to be able to prove to you that this ?s really a 
cyclone. Here is a spectrum of the region of the sun 
near the limb, and here is the hydrogen line. It is clear, 
if what I have said is true, that the incandescent hydro- 
gen is there receding from us.because the line inclines to 
the red. It is evident also, that in this case, when we 
get the line widened out towards the violet, it is 
coming towards us ; therefore we have the thing travelling 
in both directions. It is obvious to you, I think, that if 
the slit enabled us to take in the whole cyclone, we should 
get an indication of motion in two directions ; we should 
have the line diverted both towards the violet part of the 
spectrum, in the case of the hydrogen rushing towards us, 
Fic. s5.—Shifting of the F line in a solar cyclone.’ 
and towards the red in the case of the hydrogen rushing 
away from us in this circular storm, and the extreme 
velocity will be determined by the extreme limit to which 
the hydrogen line extends. In this case, the storm was 
moving with a velocity of something like 1c0 miles a 
second, which, I dare say, strikes you as somethirg 
terrible ; but if you compare the size of the sun with that 
of the earth, I think you will see it was nothing very 
wonderful after all. 
In further evidence of the truth of this, the last appli- 
cation of the spectroscope, I will show you two pictures 
of solar prominences 27,009 miles high, drawn at an 
interval of ten minutes. Here you see, first, the promi- 
nence as it appeared at a particular time on a particular day 
in March 1869 (Fig. 56). I wish to call your attention to the 
left-hand portion of the prominence, which you see is pretty 
straight. In ten minutes afterwards the whole thing 
Fic, 56.—Prom‘nence observed March 14, 1869, 11h. 5m, 
changed, and, as you see by the next picture (Fig. 57), the 
nearly straight portionis quite gone, Thatwill give yousome 
idea of the indications which the spectroscope reveals to 
us of the enormous forces at work in the sun, merely as 
representing the stars, for everything we have to say 
about the sun, the prism tells us—and it was the first to 
tell us—we must assume to be said about the stars. 
I have little doubt that, as time rolls on, the spectroscope 
Fic. 57.—The same prominence, rth, r5m. 
will become, in fact, almost the pocket companion 
of every one amongst us; and it is utterly impossible 
to foresee what depths of space will not in time be gauged 
and completely investigated by this new method of 
research. 
J. NORMAN LOCKYER 
