The Virginia enterprise. [volume] (Virginia, St. Louis County, Minn.) 1893-19??, 1897-02-05
lnfiniteSimal Lines,

Think of ruling machine that will
make 125,O0O lines in 4 square inch,
Just such an invention is in active opera
ton at Johns Hopkins university at Bal
ttimorcc. 1t is one of the most remark;!~
bic pieces of mechanism in the world,
and there has never been anything in
vented that can accomplish anything like
the task " hich it sets itself to do and
does easily. The practical, everyday
name Of the invention is "a dividing CHI
ginc.'' 1t is used by the scientists to
make gratings for sDectroscopcs. 1t does
it's work generally on spectrum metal,
and the dainty point with which it makes
infnitesimal marks is q diamond of the
very best quality. There are three
''notches' at which this machine can be
set. At the first it makes $4,000. at the
second 10000 and at the third 125,0OO
lines to the inch.
The ruling machine is used in the phys
zeal laboratory in Johns Hopkins univer-
sity. The gratings made by the ma
chine We're used in making the now ia
nous series of photographs of the solar
spectrum that We're made in the physical
laboratory of Johns Hopkins UNIVERSE
ty. The gratings used in this instance
radius. having 10000 to 10000 lines to
the inch. So absolutely correct in pre-
cision were these lines that the spectrum,
as photographed, was normal and of the
same scale throughout. The focus re-
manned automa tically adjusted, so that
experimenting the Photographic process
to do was to move the instrument to the
part of the spectrum desired, then absorb
the everything Spectra, and put in the pho
tographic plates.
Negatives Of photographs taken in. this
manncr, selected from wide range,
have been enlarged, and the result proves
cru Oil I,,c nrat oil }r
show how greatly the marvellous work
of this little machine has aided science.
Everybody knows that absolute accuracy
is an essential which no scientist can
overlook for q minute.
Therefore it is that the ruling machine,
the marvellous power of which has been
so successfully demonstrated, has at once
stepped into the front rank of the me-
chanical aids to the wondrous minds
that are laying bare the secrets of the
heavens to 4 wondering world.
In order to obtain absolute accuracy in
photographing the spectrum from era"
tings such as referred to. the negatives
measured from one standard line to an
other on dividing engine so that the
constant of the dividing engine is known.
To obtain a scale of accuracy and clear
ness, the ruling is made on a piece of
French plate glass, this glass being coat
ed with backened collodiO-chlOridc. Then
the negatives are clampel to the scale
firmly, after being adjusted into position
by the standards. After this they are
placed i'll the enlarging apparatus, and
then enlarged two and a half to four
times. Here is where one of the most
marvellous tributes to the new machine is
mathema tically made. In the negatives SO
far examined the scale has actually been
found to have been placed within one
one hundred thousandth wave length of
its true position.
An effort was made not long ago to
institute rigid comparison between the
maps of the solar spectrum resulting
from photographs from the gratings
made by the ruling machine with other
maps of the spectrum made by ordinary
measurement and drawing. The task
was abandoned for. the simple reason
that no comparison is possible, SO great
was the measure of accuracy in favor of
the work whose foundation was made by
the little machine with the diamond
point Summed up, the result of this
machines work has been to practically
place the solar spectrum itself before the
student. There is no drawing. distorted
and full of errors of wave length and in
tensity. In the first place it will be seen
the measurements are accuracy itself.
Then the photograph is the work of the
sun itself. Combine absolute accuracy
with the action of tho sun in this respect
and the combination can never be
equaleu, to say nothing of exceeding it.