Shepherdstown register. [volume] (Shepherdstown, Va. [W. Va.]) 1849-1955, 1915-02-18
The Making OF A Microscope.

The microscope has grown from sim.
pie magnifying glass into complex o
lenses and means OF adjustment that has
enabled trained eyes 10 discover world
OF infinitesimal things undreamed OF be-
fore the instrument was perfected. So
extensively is the compound microscope
now used that one OF the manufacturers
in Germany recently made his one hun
dred and fifty thousandth instrument.
There is nothing remarkable about the
stand on which the lenses are mounted
except the extreme accuracy that the
sixty o. seventy parts demand; hence
the finishing OF ii must be done by hand
Nearly one hundred screws are used in
the stand alone, and some of them must
be turned so exactly that an error gilmore
than one five-thouSandth OF an inch spoilS
the screw. One interesting process is
the "truing" OF the brass tubes. They
are first formed as nearly as may be oi
the right size and thickness then they
are pulled by powerful machine over
steel rod set in a hole in a steel plate.
The space between the rim OF the hole
and the rod determines the thickness oi
the tube, which is heightened and har-
dened by the operation, and made straight
and uniform in thickness.
The making OF the lenses is still more
important. The glass, which is the very
best of "lead flint" is received from the
glasSworkS, in small slabs and bricks.
The workmen split the slabs into pieces
OF any required size by small circular
saw that has diamond dust hammered
into its edge for teeth. Next the men
clip the detached piece into a circular
form with shears, and hold the rough
block on horizontal grindStone until il
is worn down 10 a smooth disk OF the
proper size and thickness. After that il
must be ground 10 a certain degree oi
either convexity or concavity, according
10 the service it is 10 perform. That the
men do by pressing il on a rounded
grinder If il is 10 be concave, or within a
cup-shaped one if il is 10 be a convex
lens. The grinders revolve horizontally
at high speed. Large lenses are held in
the fingers, but small ones are held IN
convenient holders, sometimes in cluS-
tiers. The workman aScertains that the
proper curvature has been reached by
measurements, and does his work so ex-
ac;ly that very few lenses iail TO pass the
first test.
The right form having been obtained
the lens must next be polished on buii
wheels until ii is transparent; and here the
strictest attention and skill are required
A high-power lens is useless unless
it brings the rays OF light that pass through
il TO an absolute focus. Any irregularity
in the curvature OF the leHs will interfere
with that, because the rays OF light vii
bend at different angle there than else
where, and blur the image OF the obiec'
before the lens. How delicate this par
OF the process is you can Judge from the
fact that big lens, such as is used in an
observatory telescope, can be spoiled il
a man drags his thumb roughly across it:
surface.
Finally the lenses are tested and ther
mounted in the microscope. For the
complete instrument you must in some
cases pay ,0OO-almost altogether fol
labor and skill, for the materials OF the
exquisite apparatus cost very little.