Blackfoot news. (Blackfoot, Idaho) 1891-1902, 1897-11-20

y
This news calls
fresh attention to
unique. almost unknown and re-
markable piece Of machinery. the ruI-
Ing engine Of professor Of Johns Hon
Ens university, wherewfth an inpor-
@snt part Of the instrument lust men
TONED was made. The object Of q spec
troseope sE 70 analyze light from a star.
nebula. the sun or some other luni-
nous object In this Operation the i'm
age o. a narrow slit is expanded side
ways until IL Is converted into a long
pr1smatic band or spectrum, violet al
one end and red AZ the other. For
studying most Of the heavenly bodies.
glass wedges or prisms are employed
70 perform the work. These, properly
arranged. will render good service
where high dispersion" or magnih-
estisn is not desirable But with the
sun. whose light is 70 intense that fl
VIII stand great dfIution $50 20 speak,.
Tar more considerable dispersion IL
entirely feasible. and the astrononi-
cal Epectroseopist is anxious to produce
this effect. in order more completely To
separate cross lines il the spectrum,
which are ordinarily too close together
70 be properly distinguished. The
whole point Of certain researches de-
pends altogether on the possibility Of
identifying a suspected line positively
and Of measuring its position ia the
Spectrum with precision. Such separs-
tion can be much better obtained with
q grating" than with a prism. There
are two kinds Of gratings. One con-
eists Of glass. on whose surface a Sc
rtes Of fine, parallel lines are ruled. The
other Il highly polished metal plate.
similarly engraved. The former lets the
light shine through #, the latter re-
fleets II. In either case the effect il
70 produce spectrum exactly as
prism does To the metal plate a slight
eoneavity is previously impaired. so
that IL will focus the image without
use Of an extra lens. Il Is the latter
type Of grating which was now intro
dueed into the new spectroscope. Bras
hear made the mirror. gave IL inst
enough curvature 10 make the focal dis
taree some twenty-odd feet, and then
sent Il 10 Baltimore for treatment in a
laboratory there. II is stated, no doubt
with truth. that the lines on this psr-
ticular grating are so fine and 90 close
together that there are 10000 TO the
inch! 4 simple comparison will en-
able one easily 10 realize what this
means. In the majority Of books there
are from 200 to $50 leaves 10 the inch
when the covers are pressed firmly TO-
gefheT. In small minority. the ruu,-
Der will range from 300 TO $50. These
latter figures represent rather thin pa
per Nov. IL we could split one Of the
very thinnest Of these leaves into 200
layers Of uniform thickness. the mo-
duct would be equivalent to los 900 10
the inch. or little less than the num-
Der OF lines in this spectroscope graf
ing. II must be remembered. more
over. that there must be a little sraee
between the lines II one is to he dis
tinct from the other Therefore. II an
inch be divided up into 600 600 equal
parts. nine Of them would be covered
by line and spaca II is stated in
Sne Of the news dispatches that the
space was 1000. 000ths wide: from
which IL must be inferred that the line
was 5000. oO0ths of an inch wide, OF
course IL is impossible TO see such Hnes
with the naked eye. Only a very pow
erful microscope would reveal them.
But they are there, and as smooth.
Straight and regular as one can imag-
inc. The ruling engine is kept in a dark
underground, in a dust-uroof
glass case, and when In service e.
guarded against temperature changes
with almost uncomfortable caution. No
one il permitted TO enter the dungeon
at such times and only a very few nm
any other occasion. Some OF the mos,
distinguished scientists Of foreign lands
have made special pilgrimage TO Balti-
more for this purpose and have es-
teemed ii a rare privilege TO be allow
ed TO see the machine. The principle
of the apparatus. however, is very sim
pie. II is the exquisite workmanshin
on II and the extraordinary safeguards
employed while making II which make
IL a wonder. A diamond point. whose
selection occupied months OF time be-
cause of the need that It should possess
a certain prescribed shape. has been
mounted in tiny carriage that IS driy-
en- to and fro over the mirror. The car
rage runs on n set Of ways or rails
and is propelled at an exceedingly uni
form speed by means OF hydraulic
motor. After each trip the carriage is
moved little TO one side SO that the
diamond will cut its next line in
new place. This adjustment is made
automatically, at the right instant. by
a screw which is the browning glory OF
the whole mechanism