Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-10-26

fixed pIaces inside the spectroscope. They
change IRON right to left as We look at dit
ferent star. The A of one star is always 4
certain Excessively smalD distance TO thC
left B; which shows that this star is NOV
ing away from us. The A of another star i:
ALWAYS to the right OF 3, which shows thai
this second star is moving toward us.
sPECTRCsCoPIC OBSERVATIONS.
Such is the essence OF this extremely beau
tiful metrod. Ii is simple theory. 1t i:
amazingly delicate and difficult in practice
II was first applied by Drs. Higgins anC
Miller in 1866 ard il has heen steadily fol
lowed at Greenwich for many years. Prof
Nocel, Of Potsdam. formerly maze many
measures of the sort and he is now engaged
In doing the same work by photography
with great sIcccSS.
The method we have Just described has
been used to determine the motions OF few
OF the brighter stars toward or from TIE
earth. Leaving out of consideration for the
present the most recent observations OF Prof.
Voce and those at the Lick Observatory
(Which form separate group oil themselves,
we NAV ~ tha. the results attained while
they are most interesting, have been very
Disappointing in regard to precision. Fol
instance, the results Tor the motion of the
bt.rht star Arcturus obtained in Greenwich
the average is about "A miles. In 1886 the
separate results vary from "a to Il miles,
and the average for the year is about 4G
miles. The method employed is correct, but
the Difficult IA - the way of employing il
are so tS.-t that small telescopes entirely
iail give accurate results.
ADVANCE IN STELLAR SPEcTRoscoPV.
In making the designs for the great tele-
kept prominently in view, and since the tele-
scope has been in active use PROT keeler,
who has charge the spectroScopic work,
has made great number of such measures.
Il WAS expected that the large size o. the
telescope woqld vastly increase the accuracy
OF such determinations, but think none o
US were prepared for the amazing precision
of the results. There is fortunately an easy
test of accuracy. The motion of the planet
Nerus toward or from the earth can be pre-
ciselv calculated from its known orbit. 1t can
also be measured with the spectroscope. The
agre- meut OF the two results shows just how
lar the Spectroscopic evidence can be trusted.
| MIL quote our measures the motion
OF Venus made in August las. by Mr..
Keaicr:
The observed motion was rs, sS, 9.3, rs
miles per second.
Tae real motion was 81, So. So, 50 miles
per second.
The error OF the spectroscope was O.S, OIL,
IL, o. miles per second.
THE DEGREE OF ACCURACY.
That i, we may say that we can be sure
OF measuring the motion of Venus or OF
brizhy star within less than one mile per Sec
ond. The Greenwich errors are vastly
greater. For instance, tine star Arcturus,
which was found at Greenwich to be ap
preaching US at the rate of 40 odd miles per
second, is in fact only moving at the rate of
iour miles and so on. The enormous ad-
vantage the great telescope over smaller
Instruments nowhere shows bette. than in
sucH work. The observations at Greenwich
were made as well rs they could be made
with their apparatus, but the power OF Mr.
Lick 81 10 science has shown itself here
Is well IS in other fields.
1t oughs to be said that the new photo
graphic methods employed by Prot. Vogel
promise 20 give most admirable results.
These are as yet unpublished, brt they
agree 50 ar as We know them with our own
work.
MOTION OF The SOLAR SYSTEM.
These preliminary observations show the
new field which is now open in this direc-
iion. Ii We can measure how fast star is
approaching the earth We can turn the
problem the other WAY and determine how
last the earth and the solar system as q
whole Is moving toward the universe OF stars
as 4 whole. Ne shall be able to fix the
direction and the velocity of the flight OF the
solar system through space.
This is one of the problems now in hand,
and 1t Is being prosecuted as rapidly as the
lGItcd iorce Of observers at Mount HamilA
ton VIII allow. Mr.. Lick provided mag
oF /,
Us with 4 very inadequate endowment fund.
Aiier the preceding explanation the
reader will now readily understand how it
is that The spectroscopic observations made
1t Mount Hamilton have been extended TO
those distant gaseous masses which are
called nCbul@, how it has been shown that
each Of these is in motion, and how it has
been determined with what yelocities they
are moving.
THF MOTION OF NEDULE.
II would indeed be strange if these bodies.
which we krcw to be closely related to stars,
were not in rIctlCn: but all the observations
OF the most skilliu! spectroscopistS up TO
this time have been able to shOwit Indeed,
IL was hardly TO be expected. The Green
wIcG results Tor the motion of ArcIuru3 are
ten times too large, and it was clearly hope
less to expect to settle this question without
an amazing increase In the precision of the
individual measures. This increase has
been attained IN the Lick Observatory meas
ureS, and already I'm July aud August OF
this NeaT) the motions of ten OF the brighter
ne0u - have been determined. The smallest
motion Is little over one mile per second,
aud the greatest is about So miles. The
error OF each determination can hardly be
above two English miles per second.
1t thri appears that the great telescope in
the shll,tui hands of Pro keeler has re-
moved one more OF the mysteries with which
the nebulse have been surrounded It was
Theoretically certain that they would De
found Su ject to the same laws as the stars
which are sometimes, at least,) formed
from jheI- progressive condensation.
Establishes a FACT.
The theoretic certainty has now become
practical one. The motions the nebuIa
have been measured, and, as 1 have said,
one more mystery has been removed rom
them.
The Lick Observatory has been in active
existence Tor little more than two wears.
Its work extends into many fields, and much
perhaps too much, is expected OF it. Ii a
satisfaction to those officially connected with
1t to be able TO chronicle a decided step for
ward in a path which was bespt with such
difficulties that it has so lar been practically
uutr~ veled. ] hope to have made it clear
that tue path Is now open and the way
plain.
Those who wish to see a more scientific !
account IF the work Just spoken of. can find |
n fTr,V..- 4