80 
rorULAR SCIENCE REVIEW. 
the sun’s light, accompauied as it necessarily must he with the reduction of 
the light of the prominences, does not bring them into view, it may be 
asked why spectroscopic analysis should avail to that end. The formation 
of an ordinary solar spectrum is merely a mode of reducing the intensity of 
the sun’s light by dispersing it over a wider area than it would otherwise 
occupy. Hence, it is quite clear that if the spectrum of the prominences 
were similarly dispersed we should gain nothing by this mode, more than 
by any other mode of reducing the light both of the sun and of a pro- 
minence. But the spectrum of the prominences is not dis2)ersed] on the 
contrary, all the light is gathered into three fine lines. Therefore the 
spectroscope allows us to do what is not possible in any other way ; namely, 
to reduce the light of the photosphere without reducing the light of the 
prominences. Hence we are enabled to see the spectrum of a prominence 
side by side with the solar spectrum. ^ 
But now we have to record one of those singular and somewhat annoying 
coincidences which have so often marked the progress of astronomical in- 
quiry. The idea which had occurred to Mr. Lockyer, occurred also to M. 
Janssen (the head of the French expedition sent out to view the eclipse) so 
soon as he had discovered that the prominences are gaseous. The eclipse, it 
will be remembered, took place on August 18 j M. Janssen formed his views 
on the same day, applied them on the next, and thus, within thirty hours, 
solved the problem over which Mr. Lockyer (through no fault of his own, 
however, be it remarked) had been engaged upwards of two years. Janssen’s 
discover}' of the visibility of the prominence-spectra when the sun is not 
eclipsed, preceded Mr. Lockyer’s by two months. But the claim of the 
latter to the independent solution of a problem, which, so far as we know, 
he was the first to suggest, was not invalidated ; because M. Janssen’s letter 
announcing the discovery did not reach the French Academy of Sciences 
until after a full account of Mr. Lockyer’s processes had been read before 
that body. By a singular coincidence it anived a few minutes after. Without 
pretending to settle the rival claims of the English and French astronomers 
to a discovery which, if not one of the most important, is at least one of the 
most interesting, ever made, we may remark that, if on the one hand we 
cannot but admire the steady perseverance with which Mr. Lockyer clung 
to the notion which had occurred to him, and persistently pursued his ob- 
servations till they had been rewarded by success; on the other, we are filled 
with admiration at the Napoleonic rapidity with which the French astro- 
nomer grasped the bearings of the problem, conceived the mode of solving 
it, and carried out that solution to the successful end. 
( )ne interesting feature of tlie discovery remains to be noticed. When 
the spectrum of a prominence is observed by the new method, it is seen in 
direct contact with tlie continuous solar spectrum ; and thus it becomes 
p<»8flible to determine the coincidence or non-coincidence of the bright lines 
of the prominence-spectrum with any of the dark lines of the solar spec- 
trum. In tliia way it has been shown that the red lino of the former 
spectrum agrees exactly with the line c (a hydrogen line) of the solar 
spectrum ; the orange line, however, is not coincident with (though near 
to) the dark line d (the double sodium line) of the solar spectrum ; lastly, 
the greenish-blue line of the i)rominence-spectrum very nearly agrees with 
