New-York tribune., 1903-02-27
THE SUNS NOTION
Measuring the Rate Scienfafcdify-
Objects of Expedition to Chih.

The expedition which is about TO leave oah
Francisco for South America, to engage in spe-
cal astronomical work. was organized to eXteha
an investigation already in progress at the LICK
Observatory. where it began six or seven years
ago. That inquiry relates to the speed with
which the solar system is travelling through
space and is carried on by means of spectre
scopy
One problem in regard to the suns way"
the direction taken by that body. has now been
fairly well settled. Nearly century ago Tobias
Mayer found that in the quarter of the
heavens where Arcturus and Vega are the stars
seemed to be separating slightly, whereas those
off toward Sirius and Aldebaran were appar-
emily approaching one another. This change
was one Of perspective, he concluded. and meant
that the and its family of planets must be
moving toward the quarter first mentioned
Subsequent observation has substantially con-
frmed that opinion though it has located the
goal trife closer to Vega. in Lyra. than Mayer
did
The question OF velocity was more perplexing;
and though some approximation was made TO
Its solution, no satisfactory method was found
until the plan adopted by Professor W. w
Campbell at the Lick Observatory, was devised.
1t was long ago noticed that If a luminous body
which is moving away from the observer is ex-
amined in spectroscope the lines which appear
in it's spectrum will be shifted out of their true
position in one direction. whereas they are
moved to the other side II the body Is coming
toward one The same effects will be produced.
of course IL the object examined is stationary
and the observer approaches or recedes in
sequence of the earth's and suns movement.
Finally. the degrees of displacement of the
lines afforded clew to the rate of motion In
the line of sight
To take advantage OF this principle it was
necessary have a particularly powerful
spectroscope Unless the magnifying or dis
persing effect of the prisms was exceptionally
great. the amount of displacement would not be
sufficiently larga TO render measurement trust
worthy. Through the generosity of Mr.. D. o.
Mills the observatory equipped with an ex-
ceptonally fine instrument with which q great
deal of other useful and famous work has been
performed besides that here referred to. The
spectroscope was attached to the big 36-inch
refractor on Mount Hamilton, and Photographic
plates were used in combination with the two
Thus permanent records secured which
would admit Of deliberate scrutiny months or
years afterward, and which could be duplicated
for the benefit of other Investigators
Since practically all stars have a motion OF
their own, and none Of them are believed to he
stationary. it would not be safe to take any one
as landmark 1t was necessary TO get meas
urements for large number and then strike an
average. Such computation is made more
difficult by the fact that all of the bodies OBJ
served not straight ahead or behind. Most
of them lay off at all sorts of angles with the
suns path, and hence a system of discounts was
requisite
digested his data for 2S3 stars and concluded
that the sun was moving at the rate of twelve
miles or more Il second Later ODSeFNdCoitS
have raised the number OF stars to four hun
dred, without materially altering that result
At Mount Hamilton, however, some portions or
the southern heavens can never be seen. To
render the computation safe ii was desirable to
set up d temporary observatory south of the
equator and to equip 1t with special 1nstru.
ments. Mr.. Mills promised to meet the cost of
these, about 24000 and the expenses of the
proposed journey more than two years ago
The most important part of the apparatus is a
rejecting telescope. made by Brashear. The
diameter is a fraction over thirtySix inches and
its focus is 111s feet from the concave mirror.
The ratio between length and aperture is
about to 1. This is an exceptionally short
focal length, but it is especially adapted to the
kind of work for which the telescope will be
employed. The expedition goes to a lofty eleva-
ton in the Chilian Andes, and will be gone
about two years. DR.. William II. Wright, of the
Lick Observatory, is in charge.