Los Angeles herald., 1910-02-08
Delicate Scientific Instruments
Bv Frederic j. Haskin

part of a grain of dried human blood,
which has been exposed to the air for
fifty years, and show by the character
istic lines that 1t is blood-and human
blood at that. 1t can take a ray of
light coming from q star so distant
that the ray has been years in reaching
here, and divide it up in such a way
as to discover the kinds of matter in
the star from whence the beam comes.
In this way the spectroscope found
helium in the sun, ninety million miles
distant, before the chemist discovered
it hard by his own doorstep.
The spectroscope has hundreds OF
uses. some of them very prosaic. In
the Bessemer process of making steel
the object is to burn a certain percen-
tage of the carbon out of the ore. 1t
usually takes about twenty minutes to
complete the process, but if it is poured
out twenty seconds too soon or twenty
seconds too late the whole is ruined.
The spectroscope tells the exact in
stant when the proper amount of car
bon has been burned out.
A remarkable instance of precision IN
big things is the case of the great
Yerkes telescope. A star of the sew
enth magnitude appears to be 1-25O0 of
an inch i'm diameter There is q. spider
web across the object glass which Is
10000 of an inch in diameter The
problem is to move this twenty-five ton
telescope with such precision that the
star disc of 1-2500 of an inch can be
threaded upon the spider web of 10000
of an inch at all times and to keep it
moving in ppposition to the motion of
the earth.V This is accomplished by
electrical attachments of wonderful
accuracy.
The CT 9th tactir1o machines now
in use represent high type of exact
mechanism, possessing as they do the
strength of a thousand giants and at
the same time the delicacy of the hair
spring of a watch. They register at
one effort the tensile strength of bar
of iron requiring million pounds to
pull it apart. and at the next effort
tell to the fraction of an ounce how
much pressure is required to crush an
eggshell. They will test the strength
of a horsehair or that of gigantic
cable with equal exactness. This ma
chine operates on the principle of the
hydraulic press-200 grains of weight
on one platform lifting 10000 pounds on
the other.
The microtome is another remarkable
instrument of the laboratory. The per-
son who has seen the breakfast bacon
slicer in a grocery store will under
stand something of it's principles. When
the scientist wants to examine the
cross section of the little corpuscle too
small to be picked up with the hand
in ineloses it in a coating of hard
paraffine, and that in another coating
of softer consistency. Then he puts it
into his little slicing machine and is
able to make slices so thin that it
would require $4,000 of them piled on
top of one another to make a stack
l.; ;rrN, 1, oil f1,a
affine away and places the almost in
visible slice on the object glass of his
microscope.
Time measuring instruments of pre-
cision were the forerunners of all the
delicate machines of science. Ever
since man has navigated the seas be-
yond the sight of land he has needed
the most accurate measures of time in
order that he might tell his longitude
with reasonable correctness. In 1714
the English government offered 100000
sterling to the man who would devise q
chronometer so accurate that longitude
could be told within thirty miles, and
a descending reward down to half as
much for the person who could tell it
within sixty miles. In 1868 John Har-
rison, son of a Yorkshire carpenter,
claimed and was given the highest
award. Now clronometers are made
which are so accurate that they VIII
vary only a few seconds in weeks. The
usual battleship carries three chronom-
eters, and the mean time of the three
is taken as actual time.
There are machines in common use
today which make screws so small
that they appear to be but little part
cles of dust, 100000 of them being re-
ouired to fill an ordinary thimble. Yet
each of them must have a perfect
head and a perfect thread. They are
used as screws for the fourth jewel
wheel of a watch. All the operations
with them are done more by the sense
of touch than of sight. and it is mar
velous how acute the human sense of
touch may become. Some time ago a
bicycle manufacturer brought some
balls intended for ball bearings to
matchmaker to show what perfect
specimens he had produced. The
matchmaker said they were not round
and wagered that he could point out
three depressions on each ball. A
micrometer was applied and it showed
that on each ball at the exact spots
pointed out there were depressions of
less than the thousandth part of an .
inch.