Dec. 21, 1882] 
Old Hypothesis 
4. The spectra of spots and 
prominences should not vary 
with the sun-spot period. 
NATURE 
187 
New Hypothesis 
The spectra should vary be- 
cause the sun is hotter at 
maximum. 
Fact.—They do vary. 
5. The spectrum of the base 
of the solar atmosphere should 
most resemble the ordinary 
Fraunhofer spectrum. 
The spectrum of the base 
should least resemble the 
Fraunhofer spectrum, because 
at the base we only get those 
molecules which can resist the 
highest temperatures. 
Facr.—As a rule the lines seen at the base are either faint 
Fraunhofer lives, or are entirely absent from the ordinary 
spectrum of the sun. 
6. Quad the same element the 
lines widest in spots should 
always be the same 
Qué the same element the 
lines widest in spots should 
vary enormously, because the 
absorbing material is likely to 
originate in and to be carried to 
different depths. 
Fact.—tThere is immense variation. 
7. The spectra of promin- 
ences should consist of lines 
familiar to us in our labora- 
tories, because solar and terres- 
trial elements are the same. 
The spectra of prominences 
should be in most cases un- 
familiar, because prominences 
represent outpourings from a 
body hot enough to prevent the 
coming together of the atoms 
of which our chemical elements 
are composed. 
Fact.—When we leave H, Mg, Ca, and Na, most of the lines 
are el'her of unknown origin or are feeble lines in the spectra 
of known elements. 
8. From the above sketch, hasty though it be, it is, I think, 
easy to gather that the new view includes the facts much better 
than the old one, and in truth demands phenomena and simply 
and sufficiently explains them, which were stumbling blocks and 
paradoxes on the old one. 
This being so, then, it is permissible to consider it further. 
9. Let us first suppose, to take the simplest case, that the sun 
when cold will be a solid mass of one pure element, z.c. that the 
evolution brought ebout by reduction of temperatures shall be 
along one line only. 
Let us take iron as the final product. 
(3-) We shall rarely, if ever, see the darkest lines affected in 
spots and prominences, 
(4.) The germs of iron are distributed among the various 
strata according to their heat-re-isting preperties, the most 
complex at L, the least complex at A. 
(5) Whatever process of evolution be imagined, as the tem- 
perature runs down from A to L, whether A, 2A, 4A; or A+ 
B, 2[2(A+B)], or X+Y+2Z, the formed material or final pro- 
duct is the work of the successive associations rendered possible 
by the gradually lowering temperature of the successive strata, 
and can therefore only exist at L. 
10, Now at this point a very importaut consideration comes 
Fic. 5. 
Then the sun’s atmosphere on the new theory gud this one 
element may be represented as follows :— 
Assume strata A—L. 
tion of all strata from A to L. 
Then— 
(1.) The Fraunhofer spectrum will integrate for us the absorp- | 
(2.) The darkest lines of the Fraunhofer spectrum? will be 
those absorbed nearest the outside of the atmosphere. 
in. It was stated (in 6) while discussing the conditious of obser- 
vation, that whether we were dealing with strata of substances 
extending down to the sun or limited to certain heights, the 
spectral lines would always appear to rest on the solar spectrum, 
and that the phenomena would 27 ¢he maiz be the same 
II. This, however, is true in the main only, there mnst be a 
| difference, and this supplies us with a test between the rival 
