The San Francisco call. [volume] (San Francisco [Calif.]) 1895-1913, 1895-06-09

given in a simple conversational manner
without any rhetorical frills, and are al
ways fully adapted to popular comprehen-
sion. Last evening he talked first about
telescopes, then about spectroscopes, and
then about stellar, solar and lunar photog-
raphy as long series of magnificent pho
tographic views were thrown upon the
screen.
ga great deal of attention has been at
tracted at different times by announce
ments of new great telescopes" said Mr..
Barnard in opening. First, there was the
30-inch telescope of Pulkowa. Then the
36-inch telescope of the Lick Observatory
was claimed to be the most powerful pos
sible. Now the Yerkes Observatory, it is
claimed, will have the most powerful tele-
scope in the world.
"Much has been said of the prospects of
that telescope. The 40 inch object
glass has been finished, and after being
tested by Professor Durham and others it
has been pronounced perfect. Everything
now depends upon the site, and it is be-
lieyed that the site at Geneva will prove
very satisfactory. Steadiness of the atmos-
phere is the most important factor in the
use of great telescope. This is more i'm
portant than transparency of the air and it
is often found on a level plain. The
Yerkes Observatory cannot be judged in
this way until the telescope is set up.
s'Now comes the announcement that the
German Government is preparing to set up
a great refractory telescope, with an object
glass A inches in diameter. The
lens has been successfully cast. It will
have feature not found in any other tele-
scope. The objective lens is of Jena glass,
which does away with the secondary spec
trum, the most Objectionable feature of
refracting telescope. There has been much
uncertainty and difficulty with this mate
rial, because it corrodes in the atmosphere
Nv &c n1a 49,
obviated.
"The Chicago telescope is theoretically
one-fourth more powerful than the Lick
and the German one-half more powerful
but we find that the blurring and destruc-
ton of the image by the unsteadiness of
the atmosphere increases with the size of
the aperture, so that the two great new
telescopes will not be as powerful prac-
tically as theoretically. The Lick tele-
scope will ever be monument to James
Lick, as it is the first of the great tele-
scopes to make its fame. That at Pulkowa
has done but little. The planetary, spec
troscopic and Photographic work of the
Lick Observatory will stand for all time. -
The spectrum and the lines characteris-
tic of different substances which the spec
troscope reveals in the spectrum of ray
of light were briefly explained with some
of the wonderful discoveries made with
the spectroscope, such as the duality of
what had been believed to be single stars,
the direction and speed of movement of
remote visible stars and the detection of
elements in the sun which also compose
the earth.
On this line Professor Barnard explained
one of the most recent and interesting dis
coyeries with the spectroscope. This dis
coyery concerns the mysterious rings of
Saturn and was made by Professor Keller,
late of the Lick Observatory and now of
the Allegheny Observatory.
Whether these rings, 10000 miles in
diameter, were solid or composed of innu-
.merable particles free to move was dis
puted until it was demonstrated mathe-
matically that they were within "danger
limit of Saturn, that is the limit within
which no satellite could exist without be-
ing torn to pieces by the force of the planet S
attraction.
IF these rings were solid bodies the
outer part Of the ring must move faster
than the inner portion" said Mr.. Barnard,
"and if they were composed of particles
free to move, the inner portion would move
the faster. Mr.. Keller photographed the
spectrum of Saturn rings, and as you see
on this screen the lines are tilted in such a
way that they prove conclusively that the
inner portions of the rings are moving
faster than the outer portions. Hence, the
rings are not solid bodies, and Mr.. Keller
has proved with the spectroscope what
before had been only demonstrated mathe-
matlcally."
The long series of photographs OF
features of the heavens, each of which
representy tiresome vigils by expert as
tronomers, which was thrown upon the
screen, cannot, of course, be described sc
as to convey any of the interest, delight
and information To one who sees them.