Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-10-26
SECRETS OF THE SKY.
Motions of the Stars Revealed
by the Big Telescope at
Lick Observatory.
MEASURING THE SPECTRA
From Which Speed in Space is Now
Accurately Calculated.
THE SOLAR SYSTEMS MOVEMENT
Toward the Great Universe of Worlds Will
Soon be Known.
GREAT CONTRIBUTIONS TO ASTRONOMY
rwRrTrEN FOR THE prspArcH.1

WRITTEN FOR THE DIsPArcH.1
The great telescope of the Lick Observa-
tory is arranged so that it is available for
three distinct kinds of astronomical research.
1t can be used as seeing instrument to ex-
anime the features OF planet, ETC., and to
measure the distances from one star to an
other near it. It can also be used as
gigantic Photographic camera 90 feet in
length, to obtain the impression of star
clusters and nebula on sensitive plates, and
1t can likewise be employed to collect and
concentrate the luster of planets, stars and
nebula, so that their light may be advanta-
geously examined by a powerful sDeetroscope.
The spectroscope can be used for two quite
different purposes. By comparing the spec
trum of star or planet with the spectra of
different terrestrial substances we can de-
termine what terrestrial elements exist in the
atmosphere of the celestial body; or again,
after having done this, the spectroscope can
be used to measure the velocity with which
the star is approaching the earth or reeeding
from it.
MOTION IN THE LINE OF SIGHT.
1t is this latter problem that wish to
speak of in order to describe some recent
discoveries made with the great telescope.
The instrument has been used in the other
fields just mentioned with eorrespondlngly
important results, but am now concerned
with this latter field only.
Let me briefly explain how it is that the
motion of star toward US is to be deter
termined by merely looking at its spec
trum. Light is composed of myraids of
waves moving with a constant velocity
through space in all directions from a
luminous body. We see the body by means
of these waves, which enter our eye and fall
upon the retina. If there are 800, 000, ,000.-
600, 900 waves per second entering the eye
we call the color of the object red. II they ara
750, 900, ,000, ,000 900 waves we call the color
violet. If there are waves of various num-
bers between 500, 900, 000, 600, 900 and $780,
O00, 600, 900, 900 al entering the eye at once
we call the object white.
WHAT THE sPECTRosCoPE DOES.
The spectroscope spreads out the light
from the object into eolored band or rib
bon, with the red light all at one end, the
violet all at another, and with the colors
orange, yellow, green, blue and indigo ar
ranged in order between them. The white
light which we saw with the eye had been
analyzed by the spectroscope into its con.
stituents colors. Suppose we should look in
this way at star which was always at the
same distance from us; and suppose further
that we could draw pencil line across the
ribbon of its spectrum at the middle Of the
violet, for instance This pencil line would
mark the place-the color-which is formed
by light waves which reach us at the rate of
75O, 900, 900, 900, 600 waves per second. Let
US suppose another pencil line drawn above
the first just outside the spectral ribbon,
thus:
FIGURE l.