The Stourbridge Observer, Cradley Heath, Halesowen & District Chronicle.
Stourbridge, West Midlands, England, 1870-04-16 00:00:00

MR. J. NORMAN LOCKYER ON
'THE SUN."

In London, last Saturday, Mr. J. Norman Lockyer,
F. 11.5.. delivered his fourth and closing lecture at the
IRoyal Institution, on "7iO Sem." In the course of
the lecture he observed that when the flame of a com-
mon candle is examined in the same way that the sun
is observed with a spectroecope, it is found that when
the flame is in anyway disturbed gases of different kinds
Are thrown out from its interior towards its exterior.
In like manner, when from any cause disturbances are
set up in the sun, there are storms or outbursts of
luminous iron, magnesium, barium, and other vapours.
It is evident, therefore, that there are layers under-
neath the external envelopes of the sun, portions of
which layers become visible to Us whenever there is the
least disturbance. Spots being depressions in the
external envelopes of the sun, it follows that an ex-
amination of the solar spots brings the sietronomer
nearer to the centre of the sun than does the ob-
servation of any other part of the orb. On ex-
amining the spots with a spectroscope, a general
absorption of the rays of all parte of the solar
spectrum is seen, as well as a selective absorption,
the latter being especially noticeable in the sodium
lines, and the greater the pressure of the nun's at-
mosphere the thicker are these absorption lines. In
order to prove that increase of pressure, without
variation in temperature, broadens the absorption
line., Mr. Lockyer threw upon the screen a continu-us
rainbow-like spectrum of the electric light, the ilia-
' pereion being produced by means of two hollow glass
prisms filled with bisulphide of carbon. Just outside
the slit of the electric lantern, the light was made to
pass through a glass tube tilled with attenuated
hydrogen gas; the tube contained also a lump of
metallic sodium. Heat was applied to the bottom of
the tube, so as to gradually vaporize the sodium. and
the vapour was at first, of course, densest near the
bottom of the tube, rather than at the top. Tue
vapour intercepted none of the rays of the spectrum,
except a portion of the yellow, cohsequently a dark
band was cut in the yellow part of the spectrum
upon the screen, but this band was thickest where the
light had previously passed through the denser por-
tions of the sodium vapour. The appearance of this
tapering dark line, consequently proved that where
the pressure of the sodium was densest, it broadened
the dark line in the yellow of the spectrum.
Thus, the broader the sodium absorption lines pro-
duced by a sun-spot, the greater is the pressure
and quantity of the sodium atmosphere over
that spot. There are now ninny large spots
upon the solar disc, and it is a very curious fact that
they give scarcely any absorption in the yellow part of
a spectrum, showing thereby that the spots are not
alike at all times. There are, in the ordinary solar
spectrum, bright lines as well as dark ones, and he
thought that these would be fouvd to be the most un-
changeable lines in it, for the dark ones are cenetautly
varying. The yellow line, so often seen in the spectrum
of the solar prominences, was once surmised to be •
line belonging to hydrogen gas when the gas became
luminous under certain very unusual conditions, but
after meets experiments with hydrogen, tried by Dr.
Frankland and himself for more than • year, they
were unable to make the luminous gam produce any
such line. It was only on the previous Saturday, that
while he (Mr. Lockyer) was examining the spectrum
of a solar prominence, he saw the bright hydrogen
lines of the prominence disappear almost entirely,
while the yellow line retained its full luminosity and
length. It would appear, therefore, to be certain that
it is not a hydrogen line; neither is it a sodium
line, for it does not fall at the right part of
the yellow of the spectrum. Probably this per-
plexing line is clue to some new substance common
in the sun, but not yet known upon earth. A
very vabirable piper on solar physics, mice communi-
cated to too Royal Soviety by Messrs. Balfour Stewart,
De la Rue, and Loewe, set forth that the photosphere
of the sun 'eight be considered to be a plane of conden-
sation, and any changes in the pressure of the plane of
condensation, will cause very considerable changes to
take place in the spectra observed. For example,
when the preesure sit the plane of condensation of a
common candle flame is reduced by the all of the air.
pimp, a halo of blue light begins to spread outeide the
flame as the pressure is diminiatied, and at last the
candle flame will give the spectrum of nearly pure
carbon. The F line of hydrogen varies very much
when the pressure is reduced, so this line is a very
delicate indicator of the pressure of the atmosphere of
the sun. Light is composed of waves varying in
length, so that when a prominence burste out upon the
sun, and in the direction of the eye of the observer,
more waves are thrown into the eye in a secand of
time; if on the other hand, the prominence be
receding with a velocity at all comparable to that
of light, the waves avid be lengthened out, and a
smaller number will enter the eye in a second. This
variation in wave-length caused by the rapid motion of
solar flames, produceii eilersg and irregular lines in the
spectrum, and by measurement of the deflection of the
bright lines from their normal position, the velocity of
motion of portions of the solar prominences may with.
in certain limits be determined. The flames often ride
or recede with a velocity of from fifty to one hundred
miles per second, which, considering the size of the
sun, is not a very excessive rate of motion. It seems
as if the chromosphere is the outer limit of the sun,
for very little absorption takes piece outside it. and
there is evidence that the absorbing atmosphere of the
sun and the photosphere begin together. As to what
is below the photosphere, spectrum analysis gives no
information whatever, and he thought that in a sun-
spot astronomers never get below the photosphere ; he
cousidered the spots to be purely surface phenomena.
The photoephere may be g WOOUB, cloudy, or even
liquid, but certainly is not solid. He did not know
the origin of the c intinuous spectrum of the enn ; a
continuous spectrum may be thrown by dense lumin-
ous gases, as well as be white-hot solids; but it is con-
soling to be aware that it is equally unknown whether
the continuous spectrum of a candle flame is due to
solid, liquid, or gaseous matter. He would close
his lecture with a few general remarks about the
nature of the sun. The situ after all is nothing but
the nearest star ; it is also • variable star, for the
spots upon it, as proved by observations extending over
the last fifty years, are very plentiful at some periods,
and very scarce at other periods; the interval between
two maximum periods or two minimum periods, is
about eleven years. We are now in a maximum period.
There is also some connection between the spots on the
nun and the sun's family of planets, for the positions of
the planete, more especially of Mercury and Venus,
have an influence upon the area of the spots on the sun.
The sun cannot be a ball of fire, for if it were it would
burn itself out in a ridiculously short space of time,
and there is reason to suppose that it is a hot globe
now elowly cooling. If we accept the hypothesis; of
Laplace, that the sun was formed originally be the
condensation of a tremendous nebula, it is not difficult
to imagine that it is now slowly cooling; and as it had
an enormous initial temperature to start with, the
cooling will go on through untold ages until at last,
having else sited all he surrounding planets into in. mane,
it will in the end roll through space a cold dark balL
Afterwards, perhaps, it may clash against another dark
ball like itself, anti the free of the blow may be proved
by calculation to be effifieient to generate light and
heat, a new sun, and other worlds.