The Wichita daily eagle. [volume] (Wichita, Kan.) 1890-1906, 1897-09-14
TO EXPLORE SPACE
Continued from Eighth Page.)

Ol Interest 10 state OTlcIly the IcdulIlS
points in the problem. Many persons
are familiar with the fact that artificial
illumination has to be employed with
high powers of the microscope, and this
is the case because. other things being
equal. the light which sutficies 10 rem
der visible the object under ordinary
conditions of seeing has 10 do duty for
the easily increased area as seen through
the glass. This may not be the most
scientific way Of stating ne case, but
probably ii can be more easily under
stood than would be e. learned talk about
the relative quantities of light that en-
ter the eye, and II is strictly correct 10
say that the light is divided UP in pro-
portion TO the increase OF apparent area
The artificial light thrown on an object
examined under the microscope cannot
be thrown on a star or other celestial
object, but substantially the same point
Is covered by increasing the side of the
surface on whiaI its rays fall to be con-
verged to the focus near the eye end Of
the telescope. That is the use OF big
object glass. But the bigger the glass
the thicker IL must be, in order to OBJ
tain the curvature necessary for bend
ing the rays 10 a focus, and this means
corresponding loss OF light by absorp-
ton in passing through the glass, the
percentage of absorption increasing with
thickness. The two glasses which form
the Yerkes objective lens Separated by
space OF about eight inches have
total minimum thickness OF four inches,
the trown being two and half. and he
cher one and half inches thick at-the
middle Of thed isks. Roughly speaking.
these glasses will absorb about one-fifth
OF the visual rays and two-fifths Of the
rays which are most active chemically.
Besides there is a further loss by re-
Election from the surfaces OF the lenses:
so hat not far from one-third OF of the
visual Of seeing rays is lost and the 9TH
er two-thirds is transmitted for use at
the eye end OF he telescope. But compu-
tations made by Vogel, for somewhat
greater thicknesses in proportion TO
area OF the object glass. indicate that the
limit of power is not reached for visual
rays until the glass is some three times
tha diameter OF the Yerkes objective,
and for the most active chemical rays
two and three-quarters times the forty
inches OF the Yerkes objective. OF course
the total gain of light for an increase |
Of one incn in the aperture would be
exceedingly small near those limits.
CHROMATIC ALTERATION.
The great trouble with the big refract-
ing telescope. then, is the ''chroma;ic I
alteration" and this cannot be done (
away with by any means at the COM (
mand OF the optician. The object /
glasses tend ID split up the rays, in the /
same manner as * done in their passage I
through prism Nearly a century and 4
a half ago the celebrated DOllan1 dis 4
covered tha: tais might BE- o5via;ed by /
the use OF two disks Of different densi-
ties, but more modern experience mas
shown that :his is not an absolute cor
rective for The big refracto-s that can
be made now. Briefly, tha result for me
Ys-kes instrument may be stated thus;
The rays in the ultra violet portion OF
ire spectrum coma 20 focus a point
which is fully three inches farther from
the object glass than the point al which
the yellow rays come tOea focus. and l.
has been found Necessary % give the
,o!lirato OF the stellar spectr0gFapl a
-ange o fmotion OF about Elk +ncses- In
recent article IN ne As-r)-Paysical
Journal Professor Haze s-aiss thai ta.s
OF focus upon wave ieng n
.ariously hampers al classes o; spectr0-
,copic work with ne Ye-kss telescope.
,u. his ta:emsn. CT tAe difficulties en-
hardly would Se understood
~ Ire ordinary Yea der L snould. how
sver, BE- n1;ed that tae defect named 3
ID: one thai csuId be eliminated from
Ia; ins-rurnen. O. any large ons. and
hat me razzuiruds os ire detect IN
.rea.es vita TIE s.ze OK he object sissL
Hence IL appears thai in ;ais respect.
Ne E-7,i. Of u=efuine>s Il nearly reac1et
/, forty iacAes and mat II We want =
p IA nesana this IL p5Ee- Sc XII Be !
,e.-ess.ry 4, fat back IA re -stse.1ors
gaica fzcsost.e e in3efsri,e expansion
Is . s1-.s,s. -15rga II. Eitao1: co-s-
,-asatiuz asssdFzn-agz. mostly @ the
kind
REJECTING TELESCOPES.
TIE Ye-kss telescope VII be the pin
.ipaI instrument % TIE obse-Ests-y 01:
a. from ne cay one n 1sSi. = I'll
= bu, ice caies among a vas; 5gzn5sr
z instruments AT a2Dll1uces 1seig1s-es
. cJve- aS completely a. poss.5ss zoF<
long :he principal lines q ssc-O-2 1y -
a. -esAa-ca- In tA= s1r6@ = PTsse>s1r
fale. ne zvaa.z-es = us .as.ra1ze1,
re. Cd H.x1 receiving p3Es-. s3spt-
ug !. ~ observations y s3sbie sta-r
- zninz-= 5e.aG "A planes. sn1 ss,es-
i-es - c;-ez: Eza. za.5e-iag S3Eef.
-ak.rg S5sxa.e E1er--osco9-- s.11.es c.