Evening star. [volume] (Washington, D.C.) 1854-1972, 1910-09-04
IN.

length of the solar year was only approx
mately known until within century
two. Astronomers have determined with
- such precision the true length of the year
CZ that our present calendar with its inter
DY caations will continue for twenty thou
sand years with not to exceed
single day.
The perfection in the measurement of
time that the astronomers achieved resulted In the con-
structon of modern astronomical clocks. These are
surrounded by glass metal cases in which partial
vacuum is maintained. They set up in specially
constructed rooms underground vaults where they
are free from vibration and where temperature and
barometric conditions remain practically constant
clock in the observatory at Berlin has for months
under these favorable conditions with error OF
only fifteen ne-thousandths of second and a maxi
of thirty onethousandths of a second day.
The winding of these clocks is done automatically by
electricity to disturb the and some
instances the winding is done frequently once
every minute
Dividing the Circle
THE division of the circle and the measurement OF
angles have ever been among unsolved problems
of the astronomer and instruments designed and
made to do this work are among the most delicate
and exact made by man. The first circular
dividing engine made in LAO by Henry Hind
ley of New York, for cutting the teeth of clock
Wheels and of the several engines constructed later
the most successful for long time was made by
Ramsden in IVY This engine was automatic in its
movements, and was made specially for graduating
circles.
But the perfection required in the graduation of cir
ces for astronomical instruments makes all these past
ment it necessary that the spindle carrying the
master plate should be nearly round and as closely
fitted in its bearings as possible Tor the degree OF ex
cellence with which that work is done determines how
closely circle can be divided
These instruments have been constructed. and their
degree of mechanical refinement may be understood IN
study of the spindle alone. This spindle four inches
in diameter at its largest part and apes to
of inch at the foot This made nearly round
and closely fitted in its bearings that movement
of thousandth of inch in out of its bearings
will in it to turn with difficulty. and In
the other with perfect freedom.
The accurate division of the circle the exact marking
of time, and the standardization OF length measure
ments may of little practical value at FIRST but
upon them depends the of whole industrial
and commercial life Modern ships could not navigate
the seas without danger if these delicate instruments
had not first been made help Captains to determine
their positions in latitude and longitude within few
miles. Railroad timetables would all 60 wrong II as
Economical clocks not regulated all over the world
within a fraction of a second. One-half the world
might otherwise lose day, and another gain as much
in time. The construction of all machinery is de-
pendent upon the OF instruments IN measuring
circles and angles Without such instruments the build
ing of ordinary gas steam engine would be diff
cult problem
We thus find the highest refinement OF mechanical
science in laboratories and experimental stations and
the instruments employed there represent the greatest
achievement of the human mind IN the field OF inven-
ton Their bearing upon the wider world of industry
and commerce is nconceivably great Great our adj
mraton be for the machine that cuts and stamps
designs out of metal automatically makes screws.
nails. tin must be greater for the delicate
stuments that make possible the construction OF the
great utility machines which have converted towns and