Evening star., 1937-01-05

Rainbows 10000 miles long and great
lets of flaming gas which shoot TO
heights of 100000 miles at speeds OF from
60 to ITO miles a second are some OF the
solar fireworks revealed by the first mo-
ton pictures ever taken OF the surface
of the sun, as reported to the National
Academy of Sciences here by Drs. Robert
r. McMath and Edison Petit OF the
University of Michigan.
These pictures were made at the new
solar tower of the Michigan University
Observatory. The astronomers described
the tower as "a telescope for solar work
where the telescope parts remain fixed
in a vertical position, with an arrange
ment of moving mirrors at the top OF
the tower which follow the sun In Its
course across the sky"
The tower Is SO feet high and rises
above a concrete well IS feet deep. At
the bottom of the we'll, where the depth
in the earth gives protection against
changes of position. or temperature, IS
spectroheliograph - device which
spreads the light of the sun into spec
trum, from which any suitable element
or wave-length of an element may be
selected for photographing.
BY this device all the rest of the bril-
liant light of the sun. which otherwise
would blot out the picture, is eliminated.
Until the invention of the Spectrohello-
graph, observation of the suns promi-
nences was possible only when a solar
eclipse gave a screening effect. The
motion pictures taken by the two Michi-
gan astronomers show the flames, which
contain large proportions of incan-
descent calcium and hydrogen, squirting
to heights of $4,000 to 100000 miles.
Along these Jets occasionally move
masses much like the discharge from a
giant Roman candle, with each a thou
sand miles long and 800 miles in diam
eter. Also shown by the motion pictures
are faint clouds which form high in the
solar atmosphere, descending in jets or
curtains, at temperatures estimated to be
near 10000 degrees F.
One of the pictures obtained shows q
gigantic rainbow arc, the bases OF which
may be 10000 miles apart. Enlarge
ments of the arc, like beads on string,
run down from its summit In both dl-
rections. The surface of the sun has
been shown by the low. sharp pointed
prominence flames darting up for per-
udRS d tllOuSdIlQ IllACS aiAd 90 HuASAAJ
subsiding. Occasionally large area OF
such low flames over an extent OF per-
haps 100000 miles seems to be blown to
one side, much like fire In a field OF
wheat.
Another significant astronomical de-
velopment reported to the National Acad-
emy is the production of a ruling ma
chine to produce difiraction grating with
as many as 270,OOO parallel lines to the
square inch, as described by DR.. Henry
Gordon Gale of the University OF Chi
cago. The production Of such gratings
is considered one of the "flne arts OF
science.
The parallel lines on the diffraction
gratings act in the same manner as a
prism in breaking light into its spec
trum. A glass prism which would pro-
duce the same result as q six-inch grating
would be impracticable, because it would
have to be 80 feet on side, thickness
which would cause 1t to be opaque. The
gratings are made Of speculum metal, a
combination Of copper and tin.
The form Of ruling machine which DR..
Gale has perfected was invented by the
late DR.. A. A. Nicholson Of the Uni
versity of Chicago. His device was un-
certain in its performance, so that he
once wrote about it: "One comes to re-
gard the machine @ having Q person.
ahtv-I had alnaoGt a1ad . feminine pr.