April 20, 1882] 
NATURE 
575 
ished, and we got two new lines continued through 
a very long series of observations without any iron 
line at all; and these two lines have no Fraunhofer 
lines corresponding with them, nor do they appear 
in the spectrum of any chemical substance.! These phe- 
nomena are the Jast which one would expect. We can 
understand that differences in the quantity of the iron 
vapour present would make a certain difference in the 
spectrum ; but we are driven to something quite indepen- 
dent of any change im the quantity of the iron vapour 
present. What, then, are we driven to? We see with 
every increase of temperature, passing from the general ab- 
sorption of the sun to the absorption of the spots and to the 
radiation in the flames, increased simplicity, just as if a 
chemist were to talk to us about the action of temperature 
on substances which he has under control, and say the 
function of temperature was to simplify. Why, then, if 
that if we are dealing with bells struck in different ways, 
however much the spectrum may vary, the molecules 
|should be going with the same velocity. We found, how- 
ever, when we came to make these observations, that the 
ibells were going with different velocities ; so that it 
cannot, by any possibility, be the same bells which on 
being struck give us those various notes. In another part 
of the spectrum these motions have been observed with 
very much greater success, for the reason that in that 
other part there are more lines which are observed to in- 
(dicate considerable motion in Sun-spots. Limiting our 
observations to lines visible in the same field of view and 
at the same moment of time, it is a mere toss-up which 
line of iron shows a descending motion of thirty miles a 
second, and which line of iron does not move at all, either 
up or down; so that I think we are justified, so far as 
7 See vol. xxiv. p. 368, Fig. 39. 
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this is the result of the working of temperature, why should 
not this simplification be due to the breaking up of the iron, 
if such iron exists at the exterior of the sun’s atmosphere, 
into its finer constituents, as by the solar currents this 
iron is carried down into more highly heated solar regions ? 
It has been stated there is no necessity for any view of 
this kind, but that the molecules of iron give out these 
vibrations, just as a series of bells vibrate differently 
according as they are struck in different ways. For- 
tunately, however, we need not have remained so long 
in doubt on a matter of this kind, because, as early as 
1869 observations were made which showed that when the 
sun is in an excited condition iron vapours are among 
those vapours which show their motion by a change of 
refrangibility. So that we had the opportunity of learning 
whether these really were identical bells, so to speak, being 
struck in different ways. I think you will acknowledge 
FG. 3.—Prof Newcomb’s observation (pp. 103, 104). 
these observations go, in considering that there is great 
probability in favour of the view that we have in these 
lines, seen in spots and storms, the lines due to the con- 
stituents of iron, and not to iron itself, which are competent 
to resist the transcendental dissociating energies of these 
hotter parts of the Solar atmosphere. If so, we can bring 
it to the test ; for if we accept any theory of evolution at 
all, we must imagine that, as our own Earth has cooled 
down, the Sun is cooling down ; and if chemical forms are 
produced by that cooling, the complexity must be in- 
creased by reduction of temperature. If that be so, every 
reduction of temperature will be accompanied by increas- 
ing complexity of chemical forms, and then the highest 
temperature will be that condition in which we shall have 
the smallest number of elementary groupings of early 
forms. Dr. Huggins’s work on the stars entirely justifies 
that view ; and I want to point out the kind of test to 
