Evening star., 1926-04-25

checked. Across the room Is a device
which shows that this mysterious
thing called electricity really has an
atomic structure.
You turn on a current and observe
the shadow OF metallic star cast by
the discharge Of negative electrons.
Now you turn magnet near the tube
in which the stream Of electrons is
flying, and notice how the stars
shadow shifts and changes with the
changing position of the magnet, just
as streams Of iron particles might do.
By another magnet arrangement you
can see how positively charged ions
are also affected, but much more slug
gishly, showing their heavier mass.
NOW grid your ina ginaiion for the
farthest flight in spice 1t has
ever dreamed of taking. you cannot
otherwise appreciate the discovery,
which this long boxlike affair before
you illustrates.
A year ago or more. every lover or
astronomy was thrilled by the an
nouncement from Mount Wilson,
Calf, that DR.. Edwin Hubble had
found definite proof that the spiral
nebulae were really island uni
verses" 1t was far from being a new
idea. More than a century ago Her
shell had suggested it and had In fact
coined the phrase island universe.
But in recent years the evidence had
seemed to be pointing away from the
theory.
But before we go farther, just what
are the spiral nebulae"?
Briefly, they are. apparently, whirls
Of misty light, as il some giant hand
were stirring a nebulous. cloudy mass
into a whirlpool formation. Seen
through a telescope some Of these sky
whirls are great wide patches Of light.
some are nothing but small misty
circlets. Some are turned broadside
on toward us. some are seen edgeWise.
some a various angles.
But aside from their peculiar struc-
ture. that which sets them off from all
other heavenly bodies is their distribu-
ton through space. All other stars
and star groups are found thickest in
the Milky Way or in its plane. AS we
search the skies farther and farther
from the Milky Way the number OF
these stars decreases.
But in the case Of the spiral nebulae.
the opposite is true. There are none
at all in the Milky Way plane. but
they grow thicker and thicker as we
so farther from it, and they cluser
most thickly at the poles" OF the
great sky-sphere of which the MILKY
Way is the equatorial girdle.
1t seems logical to look upon these
curious light-whirls as separate uni
verses. so immensely far off that the
millions Of stars, which made up each
one. blended into n nebulous mass. But
II was not until the giant 1-3-foot re-
flector of Mt. Wilson was turned on
the largest and brightest Of the spirals
that any separate stars could be De
tected.
Examining the edge of the large
nebula DR.. Hubble was able to sepa-
rate the cloudy mass into separate
stars. This led directly to the discov-
cry which astronomers consider as
fairly establishing the ''island uni
verse" theory.
! 1t was found that the largest and
brightest of the spirals was around
| a million light years away-that Is,
that the light from this star-group.
| travelling at q rate which would take
| it nearly twice around our earth be-
| tween two ticks of a watch, would
take a million years to reach U.S.
| How far away the fainter spirals are
can only be guessed at.
| X y X
| IRON the impossibly vast to the i'm
possibly small is but a step across
the threshold. Here is a machine
which shows you the actual track OF
! flying atomic particles.
You make the proper connections
| and look down on the glass cover OF
sort of metal cup. The bottom OF
| the cup is the end of a piston. covered
with gelatin mixed with India ink to
| furnish a black background.
| When the current is turned on the
piston moves back and forth at the
rate of about one plunge second. Be
meath the cups glass cover you see a
multitude of misty lines and dashes OF
| light, flashing on and off as the piston
moves back and forth.
| What are they? They are the track
of the flights of the smallest particles
known to man. They would have to
be magnified millions of times to be-
come visible themselves. But in their
flight. caused in this case by a beam
| of light shining into the cup from
the side, they knock off other par
ticles from the atoms of the rarefied
gas in the cup, and around these
''ionized' atoms minute drops or
moisture condense when the piston
suddenly reduces the pressures within
the cup. From the line of the drop
let's of moisture the light is reflected
| into our eyes. Thus do we see the in
visible.
While we are still in the realm Of
| the unima ginably fine let us step over
to this simple arrangement of bulbs
and metal fixtures. Press a button
, and a light appears at your left hand.
| sending out a beam which Is reflected
on to a scale in front of you.
| In a moment a far stronger light
! appears at the far end of the table.
AS its rays are focused into a metal
tube in the tables center the reflected
beam from the first light moves sew
eral inches along the scale.
| Nothing dramatic about that. you
say? But wait. What you have seen
Is the fairy-like push of light itself.
! And the weight of that push, in turn
| ing a delicate mirror and moving the
reflected light-beam along the scale.
is something like one-two billionths of
| an ounce!
IT SWITCH off the light and then
- touch another switch and 10! all
about us is a weird blush haze, sim
ply made to order for magic and all
sorts of hair-raising deviltry. 1t
comes from a tall glass tube standing
upright in front of us and glowing
with violet-colored light.
See the buttons on my shirt.front.
They are all a-gleam with a pale phos-
phorescent illumination. Your teeth.
when you smile. shine out as II paint
ed with luminous paint. The bright
colors of your clothing have taken on
the strangest hues.
This is the famous ultraviolet light
of which you have read so much,
which turns the values of ordinary
light topsy.turvy. We do not yet
know all its gruesome. witch-suggest-
ing properties.
The sunlight seems a bit strange
when we come out from gazing down
the long aisles Of scientific discovery
fnr which these many mechan!sms are