The sun. [volume] (New York [N.Y.]) 1833-1916, 1905-08-27

light waves. and the spectrosc cope must BIZ
properly attuned and adjusted to receive
it. permanent record of the message il
made on the Photographic plate, and after
the astronomer has learned the code he
can decipher the photograph and explain
its meaning.
THE SUMS ATMOSPHERE.
This Interpretation shows the wonderful
differences between the atmospberes Of
earth and SUN. The earth's consists mainly
of the gases hydrogen, oxygen and nitro
gen, the suns Of these gases and great
many others like iron and calcium, which
at the ordinary temperatures Of the earth
are solid, but at great heat Of the sun are
turned into gaseous form.
Furthermore, the speotroscope gives us
the means Of measuring the height that
these gasss extend above the sun, and
we find that hydrogen, helium and such
light gases rise about 1000 miles above
the suns surface. While iron. nickel, &C..
cannot be seen higher than about 500 miles.
The spectrosoopes that will 60 to Spain
with the observers OF the United States
Naval Observatory are the most powerful
that have ever been used at an eclipse
The -gratings" that these instruments arc
made Of are a product Of American inven-
ton, skill and ingenuity.
A grating is made by scratching with
fine diamond point on q polished plane or
curved surface a great many lines parallel
and equidistant and very close together.
One instrument that the writer Is going to
use has II, coo lines to every inch, and the
allength Of the diamond scratches makes
up q distance Of five miles.
The mechanical difficulties in the way Of
making a perfect grating are very great
for the reason that the separate scratches
Of tho diamond must be always exactly the
same distance apart. Where the linee are
80 close together this is very difficult to
attain, and as a matter OF fact there is
only one place In the world where gratings
are successfully ruled, and that is the Johns
Hopkins University, Baltimore, and this,
too. in spite Of the fact that all the best
mechanicians in this country and Europe
have attempted the problem.
AMERICAN OBSERVERS IN SPAIN AND AFRICA.
II the weather on Wednesday is favor
able a great many valuable observations
will be made in the few minutes that the
sun is totally eclipsed. The astronomers
representing the United States Govern
ment sailed about the beginning Of July
in the United States ships Minneapolis
Cesar and Dixie. The expedition is under
the direction Of Rear Admiral Colby NJ.
Chester, superintendent OF the Naval OBJ
servatory.
At the central line in Spain will be Prof.
W. s. Eichelberger Of the Naval Observatory,
DR.. s. A. Mitchell Of Columbia University
and Prof. r H. Bigelow Of the United States
Weather Bureau, and in Spain at the edge
Of the moons shadow path will be
g. II. Peters and G. A. Hill, both OF the
Naval Observatory, while in Northern
Africa will be found l.. E. Jewell Of
the Johns Hopkins University. Prof. N.
f. Gilbert OF Dartmouth College and
w. w. Dinwiddie of the Naval Observatory.
But after all Ia said and done, what Is
the purpose Of all these observations and
expeditions? What wonderful information
is there to gather from the sun to cause
this expenditure Of time and money?
The sun is the source Of all the light and
all the heat that we get, and the sustenanoe
OF our very life itself. 1t ia surely Of i'm
portance TO know how this light and heat
are maintained. 1t il the endeavor to
ieaTn Cne pdSt, present. anu IuVuro Oh tne
SUN that makes the astronomers 20 on
these long eclipse expeditions.
PRACTICAL GOOD FROM STUDIES OF EcLIPsRs.
Butt it might be asked again, CW bono'
What practical good is 1t for us to know
the conditions on the sun, which the a.
tronomer tells lis Is 90 many millions o!
miles away The practical good comes
from our understanding better the oondi-
lions here on earth.
Within the last year or two Prof. 8. P.
Langley, the secretary OF the Smithsonian
Washington. aided by Prof.
c. g. Abbot, has shown that the sun IL not
always sending out the same amount Of
heat. but that this heat at times b greater
than at others. Further, he has besn able
70 show by figures that do not admit Of